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Article

Colors Inspired by Nature Analyzed in Two Residential Buildings Designed by Victor Horta

Faculty of Architecture, Wrocław University of Science and Technology, Wybrzeże Stanisława Wyspiańskiego 27, 50-370 Wrocław, Poland
Submission received: 27 July 2021 / Revised: 16 August 2021 / Accepted: 26 August 2021 / Published: 31 August 2021
(This article belongs to the Special Issue Color in Architecture: Theory and Practice)

Abstract

:
The aim of the article is to present the results of research on colors carried out in two residential buildings in Brussels, designed by Victor Horta: The Tassel House (1893–1894) and The Horta House (1898–1901), representing the Art Nouveau style for which the main source of inspiration was nature. The purpose of the research was to check whether the selection of colors in the buildings was also inspired by nature. The investigation applied methods of archive studies, literature review, field survey and comparative analysis of 251 color samples taken in the interiors and façades of the two houses, compared to the 307 color samples collected in the natural environment within the radius of 700 m from the two locations. The samples were described using the Natural Colour System® chart. The research results revealed that the value of the color-matching indicator for the comparison of the color samples collected in the two examined buildings and the samples of predominant colors observed in the natural environment was determined at the average level of 92.5%. The conclusions from the study confirmed the significance of drawing inspiration from nature in the field of colors selection in the two analyzed buildings designed by Victor Horta.

1. Introduction

The first two decades of the 21st century brought significant progress of knowledge in the field of natural sciences as well as a growing interest of all aspects of the natural environment. Several scholars analyzed the relations between nature and architecture (Agrest 2018; Widera 2018) and the changing perception of nature (Goodfellow 2019; Lovelock 2016; Sigurðardóttir 2020).
The research described in this article addressed the topic of color in architecture with a special focus on the inspirations driven from nature. The article presents the results of the study on colors carried out in two townhouses and designed by Victor Horta: The Tassel House (1893–1894) and The Horta House (1898–1901). Victor Horta is regarded as the protagonist of Art Nouveau in architecture, while the edifices selected for the research represent excellent examples of Art Nouveau, the architectural style for which the main source of inspiration was Nature.
Both heritage buildings selected for color analysis are located in Brussels, in two neighborhood districts: Saint Gilles and Elsene. The distance between the two buildings is approximately 700 m. Therefore, these two districts determined the area of the study. The specific purpose of the research was to check whether the selection of colors in architecture and interior design in the two analyzed edifices was genuinely inspired by nature. The investigation applied methods of archive studies, literature review, field survey and comparative analysis of color samples taken in the two houses, being the subject of research. The samples, taken both inside and outside the residences, were compared with the color samples collected in the natural environment within the defined research area in Brussels. The methodology is described in detail in the Methods section.
The archive studies and literature review were conducted and showed that while many researchers carried out analyses in the field of color in architecture (Urbanik and Gryglewska 2005; Trocka-Leszczyńska 2000; Wróblewski 2000; Słuchocka 2020), and of colors within the Art Nouveau style (Martin 2009), most of them refer to a greater extent to painting, jewelry, interior design and furniture, while they only marginally address architecture as a field of creativity. The perception of color and the difference between measured and observed color was analyzed by Fridell Anter (2000). The topics of plant motifs in architecture and greenery in Art Nouveau gardens were presented by Pudelska and Mirosław (2015).
Numerous books and papers have been written about Victor Horta’s work (Henrion-Giele 1973; Dierkens-Aubry 1990; Dierkens-Aubry 1997; Loyer and Delahaye 1998; Aubry 2005; Collette et al. 2010; Dernie and Carew-Cox 2018), including the architect’s own writings (Horta 1936, 1985), but research related directly to the colors of Victor Horta’s architecture has not been conducted so far. This allows us to conclude that the proposed approach and method of studying the relationship between the colors of architecture and the colors characteristic of nature in a given area should be considered innovative.
Nowadays, with the growing interest in nature related to environmental protection, counteracting the negative effects of climate change and deep renovation of buildings aimed at increasing energy efficiency, the theme of color in architecture is often underestimated or even ignored. However, on the basis of the analysis of color in architecture, significant conclusions can be drawn about the sources of inspiration, including their aesthetic context, and therefore, in many cases, very subjective and intuitive. The research presented in this article aims to demonstrate that nature was also the source of inspiration for the colors of the examined architectural objects designed by Victor Horta. The two townhouses were selected for color analysis due to their high artistic and historical value, excellent quality as well as consistent character and carefully conducted conservation. The distinguishing features of the two buildings are presented in the next section. However, it is important to note that both in The Tassel House and in The Horta house, the architect was able to express his creativity without the investor imposing aesthetic and financial restrictions. Such a unique opportunity resulted in exceptional projects, in which the spirit of Art Nouveau was revealed in a distinct and captivating way (especially in the Tassel House, which was the first example of Art Nouveau style in architecture). This observation also applies to the colors used in the buildings. While the general tendency of Art Nouveau was to draw inspiration from nature, it is striking how different the colors of buildings were in different climatic conditions. For example, the buildings designed by Antoni Gaudi and other Spanish architects were much more colorful than the edifices in Belgium or Germany created at the same time. Therefore, this study aims to reveal the correlation between the colors of nature and architecture in a given region, which will be demonstrated by the example of the analysis of Horta’s buildings.

2. The Object of Research

Professor Tassel’s House (Hôtel Tassel) was selected for research as the first building in which Horta externalized the features of Art Nouveau as a new trend in architecture. Horta was one of the first architects turning to nature in pursuit of a source of inspiration to emphasize the spirit of the new times. Simultaneously, he strove to combine in architecture the vivid, primal character of nature with an expressive vision of modernity, related to the dynamic development of natural sciences. In the Tassel House, Horta designed a synthetic, modern façade in which he placed stone pillars instead of classical columns (Figure 1). Their bases and heads had organic forms of plants growing out of the ground (Figure 2).
The Tassel House is located at 6, rue Paul-Emile Janson/Paul-Emile Jansonstraat in Brussels (Elsenne). The residence was completed in 1894 and due to its unique character, the building was recognized as one of the key objects determining the direction of the development of 20th-century architecture (Borsi and Portoghesi 1991). After World War II, the elegant residence was divided into smaller apartments. In 1976, the building was purchased by an architect, Jean Delhaye. Then façade was carefully restored, and the building was adapted to become a prestigious office. Nowadays, the Tassel House is the seat of the European Food Information Council (EUFIC).
The Horta House (Maison et Atelier Horta) consists of two connected edifices: The private house on the left and the architect’s studio on the right (Figure 3). The Horta House is located at Rue Américaine 22 i 23 in Brussels (Saint Gilles) and was created between 1898 and 1901. In the period between 1906 and 1911, both parts of the Horta residence were rented and afterwards the architect made some changes, such as the transformation of the ground floor of the studio to fit a garage and the introduction of a winter garden, and a terrace on the top floor (UNESCO 2000). The front façade was slightly modified in 1911, and in 1919 the house was sold to Major Henri Pinte (Musée Horta 2005). After fifty-two years, in 1961, the house was purchased by the municipality of Saint-Gilles in the purpose to organize the Horta Museum in it. The Horta Museum opened its door to the public in 1969 to be further expanded in 1973 to include the architect’s studio. All restoration and conservation works were carried out to the highest standards under the supervision of Jean Delhaye, and since 1989 were continued by Barbara Van Der Wee.
Researchers indicate that the character of Tassel and Horta houses was emphasized by the consistent selection of colors, commonly found in the natural environment in this part of Europe, which allowed the architect to accentuate the spectacular dynamism of nature (Widera 2015). Horta counterbalanced the inherently static and rigid nature of the edifice with natural curving shapes to render the home more appealing to its residents (Swofford 2010).
The use of warm shades of yellow, orange, soft red and light brown made the interiors of both buildings seem to be constantly illuminated by sunlight (Figure 4), which was additionally increased by large windows in the façade and skylights placed on the roof surface (Apostolou 2016; Widera 2020). Introducing a large amount of daylight into the rooms (Figure 5a) and giving structures, interior furnishings and decorations the biomorphic forms clearly indicates drawing inspiration from nature (Figure 5b). The same applies to creating the effect of the “vertical expansion” characteristic of the plant world (Figure 6). (Sembach 2007).
Further in the article, detailed studies of the colors of the Horta’s House and the Tassel House are presented.

3. Methods

The research aimed at confirming if the choice of colors used in exterior and interior of the two residential buildings, designed by Victor Horta and selected for the analysis, was inspired by nature. The investigation applied the method of archive studies and literature review, followed by the field survey and comparative analysis of color samples taken in The Tassel House and The Horta House (both interiors and the façades). These samples were compared to the color samples collected in the natural environment in Brussels. The trees growing in the area of the study, especially older than 100 years, were selected for the analysis and the samples were taken in February, April, June and September to cover the colors of nature specific for each season of the year. The samples were described using the NCS (Natural Colour System®) chart. For the architectural objects, the changes of color characteristics were taken into account, including such factors as color fading, renovations and interior design modifications in time. Alterations of species planted in the two analyzed gardens and in the natural environment part of the city landscape within the radius of 700 m from the two locations were also examined. This radius is indicative, not definitive, and was applied for practical purposes, i.e., to establish the boundaries of the area in which the color samples were collected during research, while the inspirations of the architect were most likely related to the wider geographical zone. However, from today’s perspective, it is impossible to determine the exact region in which the architect could observe nature.
A total number of 307 color samples was collected from the natural environment within the defined area of research. Eighty-eight of these samples were from the trees (Table A1), 96 from shrubs and creepers (Table A2) and 123 from the blooming flowers (Table A3). In the analyzed buildings, a total of 251 color samples were taken for testing. Fifty of these samples were identified in façades, precisely 26 in the Tassel House and 24 in the Horta House (Table A4). Further, 201 color samples were found in the interiors of the two edifices, with 105 in the Tassel House and 96 in the Horta House (Table A5).
Various methods of color measure were taken into account. These include spectrophotometers, colorimeters and comparative color charts (RAL, NCS, Pantone and the Munsell chart). In the first approach, a spectrophotometer was indicated as the research method. This was motivated by the fact that the spectrophotometer measures the relative amount of electromagnetic power reflected by the sample at individual wavelengths of the entire visible spectrum (400–700 nm) by recording the reflectance per 10 or 20 nm and thus providing precise information about the color of the sample (Johnston-Feller 2001). Some authors also proposed more specific methods, such as a spectrocolorimeter and a luxmeter-colorimeter (Isebaert 2016). According to Karin Frindell Anter “Within recent colorimetric research there have been attempts to find methods for ‘colour appearance’, that is perceived colour. The aim is to be able to include factors like adaptation and surrounding colours in the mathematical computing systems. However, the precondition is still that all observation situations can be controlled and adjusted to redesigned standard situations. Thus, even if such methods for determining colour appearance are developed, they are of no use for determining the colours that we see on houses under varying and uncontrollable outdoor conditions” (Fridell Anter 2000). The same author explains the difference between the nominal and perceived color, defining the inherent color as “The colour that the colour object would have, if it was observed under the standardised viewing conditions that are a prerequisite for the NCS colour samples to coincide with their specifications” (Fridell Anter 2000). Moreover, Mahadev and Henry (Mahadev and Henry 1999) developed a Hunt94 model, a method of the spectral composition of proximal stimulus measurements with the purpose to make mathematical corrections for surrounding colors. However, the authors admit that the spectrophotometric methods such as the Hunt94 model do not account for the perceptual transparency effect of haze on outdoor color appearance and therefore do not allow us to determine the colors that an observer can see in outdoor conditions.
It is important to underline that nowadays there is no precise scientific nondestructive method that would allow us to precisely assess the color changes in time. Usually, the stratigraphic analysis is applied in building conservation. The aim of stratigraphic studies on a historical object is to establish and define the chronology of the existing technological layers and historical layers (such as the basic building material, mortars, primers and paint layers). Such data provide us with knowledge about the original character of a work of art, which in the case of architectural research expands our knowledge about the original technology of execution and the original color of the façade and its architectural detail. The system of historical layers also tells us a lot about the history of the examined object, such as the quantity and quality of renovations, the presence of primary (original, from the time when the monument was created) and secondary elements (resulting from later interventions in its form or function). The obtained data, in addition to information about the monument, such as the history of the building, iconographic material and relations between residents and owners, enable a detailed conservation analysis of the historic building. However, the first stage of stratigraphic research is to make an outcrop with a scalpel and to collect a sample (a fragment of the examined historical substance) (Jaszczak 2014). Such a test is one that destroys the original substance, and it was absolutely impossible to use this method in the heritage buildings being the subject of this research. The nondestructive method applied by the author consisted of three phases:
  • The archive studies, including the original drawings and descriptions by Victor Horta (AVB/TP; ACSG/Urb.; CRMS; Musée Horta);
  • The analysis of conservation reports, especially the ones developed by renowned architects: François Loyer, Jean Delhaye (Loyer and Delahaye 1998) and Barbara Van Der Wee (Van Der Wee 1993);
  • The collection of color samples in places less exposed to solar radiation and therefore also less prone to fading.
Having carefully considered the advantages and limitations of each of the proposed methods, for practical reasons, the comparative charts were selected as the simplest, most easily available and the most adequate for the type of analysis that involved different surfaces and materials, including heritage buildings with light-sensitive materials used for interior furnishing as well as living organisms.
The NCS (Natural Colour System®) chart was used as a basic tool for comparative analysis of samples since it is a standardized color communication system with its color notations and accurate color samples. The Natural Colour System® is a scientifically based colour system that allows for accurate colour communication and a global standard for colour definition and comparison. The NCS system uses six elementary colors, which are perceived by human beings as “pure”. Since the NCS is based on how we perceive colour visually, the system allows us to describe colour on all imaginable surfaces (NCS 2021). Regarding the color estimation systems, the Kubelka–Munk method (Kubelka and Munk 1931), based on the subtractive color theory (visible) spectrum, was proposed as adequate for diffuse surfaces (Isebaert 2016). The samples in the heritage buildings were collected in situ by the author of the paper, using 80–100% daylighting and the nondestructive method of comparing predominant colors to the DCS chart.
Considerning the fact that Horta was famous for being one of the first architects who carefully designed all elements of electric lighting for the buildings (Widera 2015), 20% of the samples were also taken in artificial lighting, which is described further in the text and indicated in the adequate tables (Table A4 and Table A5).
For the comparison of samples collected in nature and in architecture, qualitative and quantitative analyses were carried out, including text mining. Finally, the standard methods for colour identification were selected for the comparative analysis as the most adequate to express the intuitive nature of the inspirations of the renowned architect and artist, who did not use any digital tools himself.

4. Results

4.1. The Analysis of Colors in Architectural Environment

The architecture of Professor Tassel’s House reveals strong inspirations driven from nature, manifested by a combination of the distinctive, primal character of nature with an expressive vision of modernity. The colors of the façade result from combining two types of stone (Figure 7a): Light beige limestone from Savonnières with a slight touch of light pink hue (Figure 7b), and white limestone from Euville with a warmer, slightly yellowish shade of white (Figure 7c). Only on the ground floor and in the frames around the door, Horta introduced a discreetly contrasting stone band of a grey-blue color (Figure 7d). In turn, the first floor was accentuated with a stained-glass window with biomorphic decorations in milky white, golden beige, sunny yellow and blue-lilac color (Figure 8). The central part of the façade is dominated by a green color with painted iron elements: Lintels, narrow vertical posts and a filigree balustrade of the balcony on the second floor (Figure 9).
The innovative functional and spatial layout of the Tassel House made it possible to separate the public zone, located in the immediate vicinity of the street, from the private part, placed deeper inside the plot. To achieve this, Horta created two buildings covered with saddle roofs, served by independent staircases, but connected by passages on each floor. The space between the buildings was covered with two skylights. Such a solution contributed to the creation of an open, bright space inside the building, as well as the establishment of a coherent, comprehensive, decorative and compositional vision, for which nature was the main source of inspiration. The decorative stairs, with steps made of golden beech wood, resembled a peacock’s tail. In the iron construction of the stairs, Horta used dynamic soft lines to entwine the pillars and rose from the structure of the stairs, smoothly turning into chandeliers resembling exotic flowers. A painting decoration by Henri Baes with undulating ornaments covered the surfaces of the walls and ceiling like tangled plant stems. Similar motifs were used in the balustrades, floor mosaics and other interior fittings. Another skylight was placed above the decorative stairs, letting in white, diffused light, thanks to which the colors seemed very natural. The passage to the highest part of the building featured an impressive stained-glass window depicting a seaside landscape and revealing the inspiration of Japanese art.
In the Tassel House, the stairs supported the proper distribution of daylight in the building. Horta successfully combined it with a perfectly designed electric light, embedded in decorative fixtures such as brass lamps rising from the balustrade of the stairs, with cups in the shape of white flowers. The use of daylight and electric light contributed to the changing color perception in interiors depending on the type of lighting. This was taken into account in the study by collecting the samples in daylight as well as in electric light.
For color analysis of the interiors, the author selected rooms, made available by the courtesy of current users for the purposes of the research, located in both the official and private zones of the house. The official part included the reception area on the ground floor, rooms situated above the entrance to the building, to which a decorative staircase led, a smoking lounge with a six-part stained-glass window on the mezzanine, Professor Tassel’s office on the first floor and an office on the second floor. The study involved the entrance zone: The main hall on the ground floor, a small vestibule on a square plan and a larger one on an octagonal plan, the wardrobe and the vestibule on the left side, lined with a white and red mosaic with floral motifs, emphasizing the inspiration driven from nature. In the lower private zone, the research was carried out in a spacious and well-lit dining room on the ground floor. Greenery from the private garden belonging to the Tassel residence, accessible through the porte-fenêtre in the dining room bay window, was also included in the analysis. This dining room served as a private lounge for the Tassels. Excluded from the research were private rooms on the first floor that are currently unavailable, i.e., the master bedroom and a small dining room on the first floor, and two smaller bedrooms on the second floor. From the Tassel House interior, 105 color samples were collected for analysis (Table A5).
In the façade of his own house and studio, Horta created a composition of light beige and white limestones, Euville and Savonnières, combined with iron, wood and glass. The most striking feature of this front was the perfect integration of construction and decoration. Both the oak door and window joinery and the decorative iron elements were warm, golden brown in color, which perfectly matched the discrete white and beige shades of limestone. Similar to in the Tassel House, Horta gave the columns a slender form with bases and heads in the shape of claws or roots. To bring the maximum amount of daylight into the studio, a large window was placed in the sloping roof covering this part. However, the most expressive component of the façade of the Horta House was the extraordinary balcony located on the first floor in the middle axis of the façade. The rounded element added to the base of the balcony created an optically light roof, accentuating the entrance area. The balcony floor, based on an iron structure with meandering biomorphic decorations, was made of frosted glass in a blurry milky white color (Figure 10a). The posts in the upper part were connected to the iron brackets supporting the bay window, topped with a terrace and its decorative balustrade in the shape of butterfly wings. The upper part of the mansard roof above the white-tiled terrace was covered with red tiles. Two dormers and a large window were placed in the roof, through which daylight entered the staircase. At the same time, the window protected the stained-glass lantern below.
The interiors of Horta house and the studio were designed to create a maximally open space. The connection of adjacent rooms was possible thanks to the construction using a system of valley arches. In this way, sunlight could reach all parts of the building, including the basement where the sculpture studio was placed. Good lighting was provided by large windows and balcony doors positioned in both façades, as well as a skylight above the centrally located staircase.
Color samples in the atelier were taken from the rooms on the ground floor, the staircase, the waiting room and Horta’s office on the first floor, as well as from the architect’s studio on the second floor. In the architect’s house, samples for color analysis were collected from the lounge on the ground level, rooms on the elevated ground floor, i.e., a large living room on the street side connected with a dining room at the back of the house and a smaller living room added in 1906, from which a passage through the glass porte-fenêtre led to the garden. Likewise, the colors of the living room, boudoir and bedroom on the first floor were examined. On the second floor, samples were taken from the rooms of Victor Horta’s daughter, Simone, as well as from the winter garden and terrace added in 1906. The study also included a staircase lined with pink Carrara marble, and a landing on the top floor connecting the residential part with the studio. In this place, filigree iron posts rose from the structure of the stairs, forming a support for the skylight with a stained-glass window above (Figure 10b). They created coherent unity with the structure of the lamps, combining structure, function and ornament. The effect of additional illumination and optical enlargement of this zone was provided by the mirrors in the shape of butterfly wings positioned in front of each other.
Color samples were also taken from the back garden and from the original pieces of furniture preserved in the building (e.g., a set of sycamore wood in the living room from the garden side, Horta’s office equipment, an armchair and chair made of lemon wood in a private lounge on the first floor, a Japanese screen in a boudoir and Cuban mahogany furniture with silk upholstery made in factories Prelle in Lyon, designed by Eugene Grasset (Verkruyssen 2020).
In the interiors of Horta’s House and the architect’s studio, the iron structural frames, stone and brick wall cladding, wooden doors with stained-glass windows and textile upholstery of the furniture were characterized by warm pastel colors, which seemed specific for a temperate climate. In combination with the sunlight penetrating the rooms, this created an astonishing, sophisticated effect. The colors in the interiors changed their shades in a precisely planned manner thanks to electric lighting designed by Horta (de la Bédoyère 2005).
From the Horta house and studio, 96 colors samples were taken. The samples collected from Horta and Tassel Houses were compared to the samples of colors identified as predominant in the natural environment within the area covered by the study.

4.2. The Analysis of Colors in the Natural Environment

For the purpose of finding out which plants were popular in the Art Nouveau gardens, including the ones in the investigated area, the author carried out in situ research, consulted botanists and searched the literature on the subject. At the first stage of the study, the analysis of natural species preserved in the area of research was carried out. The trees growing in the area of investigation older than 100 years were selected for analysis and the samples were taken in February, April, June and September to cover the colors of nature specific for each season of the year. These samples were completed by the color analysis of the most popular plants other than trees observed in the research area, namely shrubs, creepers, and flowers.
The field research was supported by the analysis of accessible databases and literature on the subject. Changes in the city landscape and biodiversity were analyzed by some authors (Fernandes et al. 2015). Pudelska and Mirosław (Pudelska and Mirosław 2015) in their study presented a comprehensive analysis of plants commonly cultivated in Art Nouveau gardens. Based on this knowledge, the author was able to confirm that most of the species mentioned by Pudelska and Mirosław were in fact present in the neighborhood gardens, including the gardens in the Tassel House and the Horta House. Moreover, some of these plants (e.g., irises, lilies, or roses) were observed in Horta’s sketches for both examined buildings. Another important source of information about plants cultivated in Brussels (including the area of research) was the Inventaire du Patrimoine Naturel (Patrimoine Brussels 2020), where particular species can be found with the detailed description regarding age and origin. As a result of the conducted study, it was found that that among the plants present in the research area, the following species listed below were the most popular and most likely to be cultivated in the period when the two examined buildings were created, i.e., 1892–1901.
  • Trees: Platanus × acerifolia, Acer negundo, Populus nigra, Populus canadensis, Betula pendula, Robinia pseudoacacia L., Acer platanoides f. rubrum, Acer pseudoplatanus L., Aesculus hippocastanum L., Aesculus × carnea, Picea pungens Engelm.
  • Creepers: Aristolochia macrophylla Lam., Vitis riparia Michx., Hedera helix L., Parthenocissus tricuspidata.
  • Shrubs: Clematis L., Syringa vulgaris L., Hydrangea arborescens L., Cornus alba L. Magnolia kobus DC., Jasminum L., Hydrangea hydrangeoides L.
  • Blooming flowers: Rosa L., Chrysanthemum coreanum H. Lev. et Vaniot, Helianthus L., Iris germanica L., Lobelia L., Lilium martagon L., Digitalis purpurea L., Centaurea cyanus L., Paeonia lactiflora, Viola tricolor L., Lavandula L., Myosotis L.
The samples were described using the NCS (Natural Colour System®) chart. Color samples were matched with the application of the Tikkurila NCS Index identification system.

5. Discussion

The results of the field research in the built and natural environment within the Saint Gilles and Elsene districts in Brussels are presented in the six tables in the Appendix A. Table A1 shows the color samples collected from the trees growing in the study area, especially the ones older than 100 years. Table A2 is composed of the color samples from the shrubs and creepers, including the blooming ones. The colors of the first two groups of plants were analyzed in all four seasons of the year. The third group represents the blooming plants and the color samples, presented in Table A3, that were gathered during the vegetation period.
The following 307 samples of colors (divided by the group of colors) were found in the natural environment in the area of the study:
  • Green—135 samples, 43.97% of all color samples collected in the natural environment: NCS S 2030-G50Y (25), NCS S 1050-G20Y (22), NCS S 3040-G40Y (16), NCS S 2010-G50Y (15), NCS S 2060-G50Y (14), NCS S 3050-G40Y (11), NCS S 3030-G40Y (9), NCS S 1005-G90Y (5), NCS S 3010-G30Y (4), NCS S 4030-B70G (5), NCS S 0510-G50Y (3), NCS S 2020-B90G (2), NCS S 3040-Y40R (2), NCS S 0565-G10Y (2), NCS S 4030-B30G (1), NCS S 2030-G80Y (1).
  • Yellow—44 samples, 1.43% of all color samples from nature: NCS S 0550Y (10), NCS S 0540Y (9), NCS S 2020-Y10R (7), NCS S 0540-Y20R (6), NCS S 1015Y (3), NCS S 0530Y (3), NCS S 2030-Y20R (2), NCS S 1015-Y30R (2), NCS S 0502-G90Y (1), NCS S 1020-Y20R (1).
  • Orange—15 samples, 4.89% of all color samples from nature: NCS S 0550-Y60R (4), NCS S 0570-Y60R (3), NSC S 1030-Y40R (1), NCS S 0540-Y60R (1), NCS S 1060-Y70R (1), NCS S 1030-Y30R (3), NCS S 0650-Y60R (1), NCS S 0515-Y30R (1).
  • Red—23 samples, 7.5% of all color samples collected in the natural environment: NCS S 1580-Y90R (7), NCS S 2570-Y90R (7), NCS S 2570R (5), NCS S 2570-Y80R (3), NCS S 2570-Y70R (1).
  • Pink—21 samples, 6.84% of all color samples from nature: NCS S 1005-Y40R (1), NSC S 1510-Y60R (1), NCS S 0502R (3), NCS S 1060-R30B (1), NCS S 1030-R30B (4), NCS S 0530-Y80R (6), NCS S 1015-Y50R (1), NCS S 0550-Y80R (2), NCS S 0560-Y80R (2)
  • Beige/white—11 samples, 3.58% of all color samples from nature: NSC S 1002-Y50R (1), NCS S 0300N (4), NCS S 0505-Y10R (1), NCS S 1000N (1), NCS S 0500N (1), NCS S 0502-Y50R (1), NCS S 0505Y (1), NCS S 0502Y (1)
  • Violet—18 samples, 5.86% of all color samples from nature: NCS S 2040-R60B (7), NCS S 1510-R40B (1), NCS S 3040-R50B (4), NCS S 6020-R30B (1), NCS S 1510-R60B (1), NCS S 3030-R60B (2), NCS S 3005-R60B (1), NCS S 7020-R20B (1)
  • Brown—21 samples, 6.84% of all color samples from nature: NCS S 8005-Y80R (1), NCS S 3005-Y50R (2), NCS S 4030-Y50R (2), NCS S 6010-Y50R (4), NCS S 3010-G90Y (5), NCS S 7010-Y40R (1), NCS S 3010-Y50R (1), NCS S 5030-Y80R (3), NCS S 3030-Y70R (1), NCS S 7005-Y80R (1)
  • Blue—12 samples, 3.9% of all color samples from nature: NCS S 2010-B30G (1), NCS S 1040B (2), NCS S 1040-R90B (2), NCS S 1030-R80B (2), NCS S 0155-R80B (2), NCS S 1030-B10G (1), NCS S 1040B (2)
  • Black/grey—2 samples, 0.65% of all color samples from nature: NCS S 7500N (1), NCS S 2005-R80B (1).
The color samples collected in the architecture are presented separately for the exteriors (Table A4) and interiors (Table A5). The following 251 color samples (divided by the group of colors) were identified in the architecture, namely in the two buildings designed by Victor Horta:
  • Exteriors (50 samples), 19.92% of all 251 color samples collected in the architectural objects.
    • Green—seven samples, 14% of samples from exteriors, 2.79% of all color samples from architecture: NCS S 2010-G50Y (3), NCS S 1005-G90Y (2), NCS S 3010-G30Y (2).
    • Yellow—seven samples, 14% of all color samples collected in the exteriors, 2.79% of all the color samples from architecture: NCS S 2030-Y20R (4), NCS S 1020-Y20R (3).
    • Orange: zero samples.
    • Red: zero samples.
    • Pink—seven samples, 14% of samples from exteriors, 2.79% of all color samples from architecture: NCS S 1005-Y40R (5), NSC S 1510-Y60R (2).
    • Beige/white —13 samples, 26% of samples from exteriors, 5.19% of all color samples from architecture: NSC S 1002-Y50R (4), NCS S 1000N (5), NCS S 0500N (4).
    • Violet—two samples, 4% of samples from exteriors, 0.8% of all color samples from architecture: NCS S 3005-R60B (2).
    • Brown—nine samples, 18% of samples from exteriors, 3.59% of all color samples from architecture: NCS S 8005-Y80R (1), NCS S 3005-Y50R (1), NCS S 4030-Y50R (3), NCS S 3010-Y50R (1), NCS S 5030-Y80R (3).
    • Blue—one sample, 2% of samples from exteriors, 0.4% of all color samples from architecture: NCS S 2010-B30G (1).
    • Black/ grey—three samples, 6% of samples from exteriors, 1.19% of all color samples from architecture: NCS S 2005-R80B (3).
  • Interiors—201 color samples, which makes 80.08% of all 251 color samples collected in the architectural objects.
    • Green—32 samples, 15.92% of all 201 color samples collected in the interiors and 12.75% of all 251 color samples collected in the architecture: NCS S 2030-G50Y (7/7), NCS S 1050-G20Y (1/1), NCS S 3040-G40Y (2/2), NCS S 2010-G50Y (9/12), NCS S 2060-G50Y (1/1), NCS S 3050-G40Y (1/1), NCS S 3030-G40Y (1/1), NCS S 1005-G90Y (3/5), NCS S 4030-B70G (1/1), NCS S 2020-B90G (1/1), NCS S 3040-Y40R (1/1), NCS S 4030-B30G (2), NCS S 0510-G50Y (1), NCS S 2030-G80Y (1).
    • Yellow—40 samples, 19.9% of all color samples collected in the interiors and 15.94% of all color samples collected in the architecture 251: NCS S 1015-Y30R (7), NCS S 1015Y (6), NCS S 0530Y (5), NCS S 2030-Y20R (4), NCS S 0540Y (3), NCS S 2020-Y10R (3), NCS S 0550Y (2), NCS S 0502-G90Y (4), NCS S 1020-Y20R (4), NCS S 0540-Y20R (2).
    • Orange—22 samples, 10.94% of all color samples collected in the interiors and 7.97% of all color samples collected in the architecture 251: NCS S 0550-Y60R (8), NSC S 1030-Y40R (3), NCS S 0650-Y60R (3), NCS S 1060-Y70R (2), NCS S 1030-Y30R (2), NCS S 0515-Y30R (2), NCS S 0570-Y60R (1), NCS S 0540-Y60R (1).
    • Red—12 samples, 5.97% of samples from interiors, 4.78% of all color samples from the architecture: NCS S 2570-Y90R (5), NCS S 1580-Y90R (2), NCS S 2570R (2), NCS S 2570-Y80R (2), NCS S 2570-Y70R (1).
    • Pink—18 samples, 8.95% of samples from interiors, 7.17% of all color samples from the architecture: NCS S 1005-Y40R (2), NCS S 0502R (2), NCS S 1030-R30B (1), NCS S 0530-Y80R (4), NCS S 1015-Y50R (6), NCS S 0550-Y80R (2), NCS S 0560-Y80R (1).
    • Beige/white—31 samples, 15.42% of samples from interiors, 12.35% of all color samples from the architecture: NCS S 0300N (4), NCS S 0505-Y10R (3), NCS S 1000N (2), NCS S 0502-Y50R (10), NCS S 0505Y (1), NCS S 0502Y (11).
    • Violet—eight samples, 3.98% of samples from interiors, 3.19% of all color samples from the architecture: NCS S 2040-R60B (1), NCS S 1510-R40B (2), NCS S 3040-R50B (1), NCS S 6020-R30B (1), NCS S 1510-R60B (1), NCS S 3030-R60B (1), NCS S 7020-R20B (1).
    • Brown—19 samples, 9.45% of samples from interiors, 7.57% of all color samples from the architecture: NCS S 4030-Y50R (6), NCS S 6010-Y50R (2), NCS S 3010-G90Y (2), NCS S 7010-Y40R (2), NCS S 3030-Y70R (6), NCS S 7005-Y80R (1).
    • Blue—11 samples, 5.47% of samples from interiors, 4.38% of all color samples from the architecture: NCS S 1040B (3), NCS S 1040-R90B (1), NCS S 1030-R80B (1), NCS S 0155-R80B (1), NCS S 1030-B10G (2), NCS S 1040B (3).
    • Black/grey—two samples, 0.99% of samples from interiors, 0.8% of all color samples from the architecture: NCS S 7500N (2).
The total number of color samples collected in the natural environment was 307 and the analysis of samples allowed the author to identify 82 colors. A total of 251 color samples were taken in the two analyzed buildings designed by Victor Horta and 81 colors were identified by the study. As a result of the research, it was discovered that all colors present in architectural objects were observed in the natural environment. The comparison of the occurrence of colors in nature and the architecture of the examined buildings designed by Victor Horta is presented in Table 1.
The only color sample detected in nature in the area of the study and not present in the analyzed buildings was an intensive shade of pink (NCS S 1060-R30B). In the natural environment, the sample was found in the Aesculus × carnea (red horse-chestnut), solely in the middle part of the flowers, during the short blooming period in May/June, which allows one to say that this particular color has been only exceptionally represented in natural conditions within the research area. The general observation was that the colors represented in a small number in the natural conditions were only marginally observed in the architecture. This refers to such groups of colors as black and grey (0.65% of samples from nature, 1.99% of the samples from architecture), and blue (3.9% of samples from nature, 4.78% of the samples from architecture). Only for the samples belonging to the white and beige group of colors was the occurrence in the natural environment (3.58%) slightly smaller than in the architecture (17.53%). This can be explained by the fact that the color samples in the natural environment were collected solely from plants and did not include any snow nor stone. The inclusion of color samples from snow and natural stone observed in the area of study would balance the 13.95% difference of the colors’ presence.
For most of the identified groups of colors, the percentage of samples collected in the natural and built environments has been very similar. The number of samples belonging to the group of yellow colors collected in the natural environment was 44 (14.3%) and in the analyzed buildings it was 47 (18.72%). The observed difference was therefore only 4%. The percentage of samples belonging to the group of orange colors collected in the natural environment was 4.89% and in the examined edifices it was 7.97% (3% difference). For the group of red colors, the samples collected in nature made 7.5% and in architecture 4.78% (2.72% difference). Similarly, the group of pink colors represented 6.84% of the samples from nature and 9.96% of the samples from the architecture (3.12% difference). For violet colors, 5.86% of the samples from nature 3.98% of the samples from the architecture resulted in a difference of only 1.88%. Finally, for brown colors, 6.84% of samples from the natural environment compared to 11.15% of the samples from the built environment resulted in a difference of 4.31%. In all of the above cases, the noted difference was less than 5%.
In relation to the group of colors based on shades of green, it was found that green samples represented 43% of all color samples collected in the natural environment and 15.54% of the color samples identified in the examined buildings. While it may be surprising that the only disproportion in the balance of colors is observed in regard to green, for which the association with nature seems perfectly obvious, in fact this confirms that the perception of colors for a brilliant observer of nature like Horta was truly in-depth and far from schematic. The fresh and intensive shade of green (NCS S 1050-G20Y), the second most frequent color observed in nature, in architecture appeared only once, in the stained-glass window in the Tassel House. In general, the most intense shades of colors, often present in nature and less frequently in architectural objects, in the analyzed buildings were observed mainly in the stained-glass windows. It concerned such colors as the shades of blue (NCS S 1030-B10G, NCS S 0155-R80B, NCS S 1040B), violet (NCS S 2040-R60B, NCS S 3040-R50B), pink (NCS S 1030-R30B) and green (NCS S 4030-B30G, NCS S 3050-G40Y). This can be interpreted as the need to supplement the range of colors in architecture with vivid hues, however, without sacrificing the elegant ambiance of the interiors and façades designed by the architect. Moreover, this interpretation can be supported by the observation that the diversity of colors used in the exteriors was 4 times smaller than for the colors used in the interiors of the analyzed buildings and the most intensive colors were used in the private parts of the residences.
Regarding the main colors observed in nature and in the architecture, the level of compliance achieved was 73% for the group of green colors (in architecture, this group was less frequently found than in nature), 86% for the group of white and beige colors (in architecture, this group was more frequently found than in nature) and a range of 95–98% for all other color samples. The value of the color-matching index for the comparison of the color samples collected in the two tested buildings with the samples of the dominant colors observed in the natural environment was determined at the average level of 92.5%. Such a high level of matching demonstrates the compatibility of Horta’s works with the overarching philosophy of the Art Nouveau style, according to which following Nature was always beneficial because Nature was considered the champion in all areas of life. In the analyzed archive materials, there is no clear declaration from Victor Horta that the architect used the palette of colors he observed in the natural environment. The inspiration driven from nature regarding color selection was rather intuitive and resulted from the Art Nouveau aesthetics. The scientific rigor applied to a subjective matter such as color perception was meant to confirm the hypothesis that the selection of colors in the two examined buildings designed by Victor Horta was indeed inspired by the colors observed in nature. Nevertheless, this observation does not solely address the closest neighborhood of the Tassel House and the Horta House. The perception of nature as such cannot be limited to an area of several hundred square meters but is much more general. While it was necessary to establish the boundaries of the research area for the purpose to collect color samples, it would be impossible to define the limits of the architect’s inspiration and imagination. However, it was concluded that the architect turned out to be a conscious and careful observer of the natural environment, who appreciated both the brilliant design solutions found in nature and the original color combinations. Therefore, it is possible to say that the conducted research confirmed the importance of drawing inspiration from nature for the creation of Art Nouveau architecture in relation to the color range used.

6. Conclusions

The research presented in this article addressed the comparison of colors of the interiors and façades of The Tassel House and The Horta House, and the color samples collected in the natural environment within the indicative radius of 700 m from the two examined edifices. This radius was used solely to establish the boundaries of the area in which the color samples were collected, and not to define the limits of the architect’s inspirations, which where most likely related to the broader geographical zone (impossible to determine from today’s perspective). The purpose of the study was to check whether the selection of colors in the buildings was inspired by nature. The investigation applied methods of archive studies, literature review, field survey and comparative analysis of the color samples using the NCS (Natural Colour System®) chart.
The trees growing in the area of research older than 100 years were selected for the analysis and the samples were taken in February, April, June and September to fully cover the colors of nature specific for each season of the year. This collection was completed by color samples from the most popular plants, other than trees, observed in the research area (shrubs, creepers and blooming plants). For the architectural objects, the changes of color characteristics were taken into account, including such factors as color fading, renovations, and interior design changes in time. Alterations of species planted in the two analyzed gardens and in the natural environment making up part of the city landscape were also evaluated.
A total number of 307 color samples, representing 82 colors, was collected from the natural environment within the defined area of research. Eighty-eight of these samples were from trees, 96 from shrubs and creepers and 123 from the blooming flowers. In the analyzed buildings, a total of 251 color samples, representing 81 colors, were taken for testing. Fifty of these samples were identified in façades, precisely 26 in the Tassel House and 24 in the Horta House. Further, 201 color samples were found in the interiors of the two edifices, with 105 in the Tassel House and 96 in the Horta House.
As a result of the research, it was discovered that all colors present in architectural objects were also observed in the natural environment. For most of the identified groups of colors, the percentage of samples collected in the natural and built environments were very similar. The colors that seldom appeared in the natural environment were rarely observed in architecture. The intense shades of colors, more often present in nature and less frequently in architectural objects, in the analyzed buildings were observed mainly in the stained-glass windows. The only color sample detected in the natural ecosystem in the area of the study, and not present in the analyzed buildings, was an intensive shade of pink (NCS S 1060-R30B) spotted in the Aesculus × carnea flowers during the short blooming period. However, it was concluded that this particular color has only been exceptionally represented in natural conditions within the research area.
Exclusively for the group of green colors, the most popular in the natural environment, it was noted that the various shades of green represented 43% of all color samples collected in the natural environment and only 15.54% of the color samples identified in the examined buildings. This has been a very interesting observation because intuitively one could define the green color as dominant in nature and the off-white and beige shades as predominant in the façades designed by Horta. Only a thorough analysis allowed for the assertion that, in fact, Horta avoided the one-dimensional and standard perception of color in nature. On the basis of the conducted research, it was concluded that the architect turned out to be a conscious and careful observer of the natural environment. He appreciated both the brilliant design solutions found in nature and original color combinations. In addition to the evocative green leaves, Horta noticed the poetic mood of golden leaves in autumn, yellow-grey stems of withering plants and a purple-pink range of summer flowers viewed in the sunlight. In the architecture of the examined objects designed by Horta, green is present in numerous shades and variants, from bright, greenish-gold painted structural elements in façades, through olive tones of wallpaper and a screen in the boudoir in the Horta House, to intensely emerald counterpoints, created by armchairs in the waiting room of the Tassel House. Interesting and unusual for Art Nouveau architecture is also the use of expressive shades of red, in relation to which the comparative analysis showed a close relationship with the colors found in nature in the immediate vicinity of the examined buildings.
With regard to the main colors observed in nature and architecture, the value of the color-matching indicator of colors samples collected in the two examined buildings and the samples of predominant colors observed in the natural environment was identified at the level of 92.5% while the minimum value was 73% and the maximum 98%. This high level of matching demonstrates the compliance of Horta’s works with the overarching philosophy of the Art Nouveau trend, according to which following Nature was always beneficial and valuable because Nature was considered the champion in all areas of life. The conducted research confirmed the importance of drawing inspiration from nature for the creation of architecture in relation to the color range used.

Funding

This research received funding from Wrocław University of Science and Technology, grant number S40203/K0107.

Acknowledgments

The author acknowledges the incredible kindness and help of Horta Museum in Brussels and European Food Information Council (EUFIC) in Brussels, as well as the professional assistance and support received from ROCAMAT (France) and in particular from Thibault Huger and Florence Dangelser.

Conflicts of Interest

The author declares no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Appendix A

Table A1. Eighty-eight color samples taken from trees identified in the research area. The numbers below the color sample provide the information how many times a given color appears in the table (how many times it appears in all natural samples/how many times it appears in the analyzed architectural objects).
Table A1. Eighty-eight color samples taken from trees identified in the research area. The numbers below the color sample provide the information how many times a given color appears in the table (how many times it appears in all natural samples/how many times it appears in the analyzed architectural objects).
ImageNameSpringSummerAutumnWinter
Arts 10 00060 i045Platanus × acerifoliaNCS S 2030-G50YNCS S 2060-G50YNCS S 0550YNSC S 1002-Y50R
Arts 10 00060 i046
6 (25/7)
Arts 10 00060 i047
8 (14/1)
Arts 10 00060 i048
6 (10/2)
Arts 10 00060 i049
1 (1/4)
NCS S 2010-G50YNCS S 3040-G40Y NCS S 0550-Y60RNCS S 2010-G50Y
Arts 10 00060 i050
5 (15/12)
Arts 10 00060 i051
4 (16/2)
Arts 10 00060 i052
1 (4/8)
Arts 10 00060 i053
5 (15/12)
Arts 10 00060 i054Acer negundoNCS S 1050-G20YNCS S 2060-G50YNCS S 0550YNCS S 2030-G50Y
Arts 10 00060 i055
8 (22/1)
Arts 10 00060 i056
8 (14/1)
Arts 10 00060 i057
6 (10/2)
Arts 10 00060 i058
6 (25/7)
NCS S 2030-G50YNCS S 1050-G20YNCS S 1580-Y90RNCS S 8005-Y80R
Arts 10 00060 i059
6 (25/7)
Arts 10 00060 i060
8 (22/1)
Arts 10 00060 i061
1 (7/2)
Arts 10 00060 i062
1 (1/1)
Arts 10 00060 i063Populus nigraNCS S 1050-G20YNCS S 2030-G50YNCS S 0540YNCS S 2010-G50Y
Arts 10 00060 i064
8 (22/1)
Arts 10 00060 i065
6 (25/7)
Arts 10 00060 i066
2 (9/3)
Arts 10 00060 i067
5 (15/12)
NCS S 2060-G50YNCS S 3050-G40YNCS S 2020-Y10RNCS S 7005-Y80R
Arts 10 00060 i068
8 (14/1)
Arts 10 00060 i069
3 (11/1)
Arts 10 00060 i070
1 (7/3)
Arts 10 00060 i071
1 (1/1)
Arts 10 00060 i072Betula pendulaNCS S 1015YNCS S 1050-G20YNCS S 0530YNCS S 0300N
Arts 10 00060 i073
3 (3/6)
Arts 10 00060 i074
8 (22/1)
Arts 10 00060 i075
1 (3/5)
Arts 10 00060 i076
1 (4/4)
NCS S 2060-G50YNCS S 3050-G40YNCS S 0550YNCS S 7500N
Arts 10 00060 i077
8 (14/1)
Arts 10 00060 i078
3 (11/1)
Arts 10 00060 i079
6 (10/2)
Arts 10 00060 i080
1 (1/2)
Arts 10 00060 i081Populus canadensisNCS S 2060-G50YNCS S 3050-G40YNCS S 0550YNCS S 1005-G90Y
Arts 10 00060 i082
8 (14/1)
Arts 10 00060 i083
3 (11/1)
Arts 10 00060 i084
6 (10/2)
Arts 10 00060 i085
3 (5/5)
NCS S 1050-G20YNCS S 4030-B70GNCS S 2030-Y20RNCS S 3005-Y50R
Arts 10 00060 i086
8 (22/1)
Arts 10 00060 i087
2 (5/1)
Arts 10 00060 i088
1 (2/8)
Arts 10 00060 i089
1 (2/1)
Arts 10 00060 i090Robinia pseudoacacia L.NCS S 1050-G20Y NCS S 0505-Y10RNCS S 1015YNCS S 1005-Y40R
Arts 10 00060 i091
8 (22/1)
Arts 10 00060 i092
1 (1/3)
Arts 10 00060 i093
3 (3/6)
Arts 10 00060 i094
1 (1/7)
NCS S 2030-G50YNCS S 2060-G50YNCS S 0540YNCS S 1000N
Arts 10 00060 i095
6 (25/7)
Arts 10 00060 i096
8 (14/1)
Arts 10 00060 i097
2 (9/3)
Arts 10 00060 i098
1 (1/7)
Arts 10 00060 i099Acer platanoides f. rubrumNCS S 2570-Y90RNCS S 3040-G40YNCS S 2570-Y90RNSC S 1510-Y60R
Arts 10 00060 i100
3 (7/5)
Arts 10 00060 i101
4 (16/2)
Arts 10 00060 i102
3 (7/5)
Arts 10 00060 i103
1 (1/2)
NCS S 2570RNCS S 4030-Y50RNCS S 2570RNCS S 2010-G50Y
Arts 10 00060 i104
3 (5/2)
Arts 10 00060 i105
1 (2/9)
Arts 10 00060 i106
3 (5/2)
Arts 10 00060 i107
5 (15/12)
Arts 10 00060 i108Acer pseudoplatanus L.NCS S 2570-Y90RNCS S 1015-Y30RNCS S 0570-Y60RNCS S 1015Y
Arts 10 00060 i109
3 (7/5)
Arts 10 00060 i110
1 (2/7)
Arts 10 00060 i111
1 (3/1)
Arts 10 00060 i112
3 (3/6)
NSC S 1030-Y40RNCS S 3040-G40YNCS S 2570RNCS S 2010-G50Y
Arts 10 00060 i113
1 (1/3)
Arts 10 00060 i114
4 (16/2)
Arts 10 00060 i115
3 (5/2)
Arts 10 00060 i116
5 (15/12)
Arts 10 00060 i117Aesculus hippocastanum L.NCS S 1005-G90YNCS S 0502RNCS S 0550YNCS S 6010-Y50R
Arts 10 00060 i118
3 (5/5)
Arts 10 00060 i119
1 (3/2)
Arts 10 00060 i120
6 (10/2)
Arts 10 00060 i121
1 (4/2)
NCS S 2030-G50YNCS S 2060-G50YNCS S 0515-Y30RNCS S 3010-G90Y
Arts 10 00060 i122
6 (25/7)
Arts 10 00060 i123
8 (14/1)
Arts 10 00060 i124
1 (1/2)
Arts 10 00060 i125
2 (5/2)
Arts 10 00060 i126Aesculus × carneaNCS S 1050-G20YNCS S 2060-G50YNCS S 0540-Y60RNCS S 3010-G90Y
Arts 10 00060 i127
8 (22/1)
Arts 10 00060 i128
8 (14/1)
Arts 10 00060 i129
1 (1/1)
Arts 10 00060 i130
2 (5/2)
NCS S 1030-R30BNCS S 1060-R30BNCS S 0550YNCS S 7010-Y40R
Arts 10 00060 i131
1 (4/1)
Arts 10 00060 i132
1 (1/0)
Arts 10 00060 i133
6 (10/2)
Arts 10 00060 i134
1 (1/2)
Arts 10 00060 i135Picea pungens Engelm.NCS S 0510-G50YNCS S 2020-B90GNCS S 2020-B90GNCS S 2010-B30G
Arts 10 00060 i136
1 (1/1)
Arts 10 00060 i137
2 (2/1)
Arts 10 00060 i138
2 (2/1)
Arts 10 00060 i139
1 (1/1)
NCS S 1050-G20YNCS S 4030-B30GNCS S 4030-B70GNCS S 2005-R80B
Arts 10 00060 i140
8 (22/1)
Arts 10 00060 i141
1 (1/2)
Arts 10 00060 i142
2 (5/1)
Arts 10 00060 i143
1 (1/3)
Table A2. Ninety-six color samples taken from shrubs and creepers identified in the research area. The numbers below the color sample provide the information how many times a given color appears in the table (how many times it appears in all natural samples/how many times it appears in the analyzed architectural objects).
Table A2. Ninety-six color samples taken from shrubs and creepers identified in the research area. The numbers below the color sample provide the information how many times a given color appears in the table (how many times it appears in all natural samples/how many times it appears in the analyzed architectural objects).
ImageNameSpringSummerAutumnWinter
Arts 10 00060 i144Hedera helix L.NCS S 2030-G50YNCS S 1050-G20YNCS S 3030-G40YNCS S 3030-G40Y
Arts 10 00060 i145
10 (25/7)
Arts 10 00060 i146
11 (22/1)
Arts 10 00060 i147
8 (9/1)
Arts 10 00060 i148
8 (9/1)
1050-G20YNCS S 3050-G40Y NCS S 3050-G40Y NCS S 3010-G30Y
Arts 10 00060 i149
11 (22/1)
Arts 10 00060 i150
4 (11/1)
Arts 10 00060 i151
4 (11/1)
Arts 10 00060 i152
3 (4/2)
Arts 10 00060 i153Aristolochia macrophylla Lam.NCS S 2030-G50YNCS S 1050-G20YNCS S 1050-G20YNCS S 3030-G40Y
Arts 10 00060 i154
10 (25/7)
Arts 10 00060 i155
11 (22/1)
Arts 10 00060 i156
11 (22/1)
Arts 10 00060 i157
8 (9/1)
NCS S 1005-G90YNCS S 0510-G50YNCS S 3030-G40YNCS S 2020-Y10R
Arts 10 00060 i158
3 (5/5)
Arts 10 00060 i159
2 (3/1)
Arts 10 00060 i160
8 (9/1)
Arts 10 00060 i161
3 (7/3)
Arts 10 00060 i162Schizophragma hydrangeoidesNCS S 2010-G50YNCS S 0300NNCS S 0530-Y80RNCS S 3010-G30Y
Arts 10 00060 i163
3 (15/12)
Arts 10 00060 i164
1 (4/4)
Arts 10 00060 i165
3 (6/4)
Arts 10 00060 i166
3 (4/2)
NCS S 1005-G90YNCS S 1050-G20YNCS S 2030-G80YNCS S 2020-Y10R
Arts 10 00060 i167
3 (5/5)
Arts 10 00060 i168
11 (22/1)
Arts 10 00060 i169
1 (1/1)
Arts 10 00060 i170
3 (7/3)
Arts 10 00060 i171Jasminum L.NCS S 1050-G20YNCS S 0502YNCS S 0502-G90YNCS S 2010-G50Y
Arts 10 00060 i172
11 (22/1)
Arts 10 00060 i173
1 (1/11)
Arts 10 00060 i174
1 (1/4)
Arts 10 00060 i175
3 (15/12)
NCS S 2030-G50YNCS S 3040-Y40RNCS S 3030-G40YNCS S 3005-Y50R
Arts 10 00060 i176
10 (25/7)
Arts 10 00060 i177
2 (2/1)
Arts 10 00060 i178
8 (9/1)
Arts 10 00060 i179
1 (1/1)
Arts 10 00060 i180Parthenocissus tricuspidataNCS S 3040-Y40RNCS S 3050-G40YNCS S 0550YNCS S 4030-Y50R
Arts 10 00060 i181
2 (2/1)
Arts 10 00060 i182
4 (11/1)
Arts 10 00060 i183
1 (10/2)
Arts 10 00060 i184
1 (2/9)
NCS S 2030-G50YNCS S 3030-G40YNCS S 1060-Y70RNCS S 3010-G90Y
Arts 10 00060 i185
10 (25/7)
Arts 10 00060 i186
8 (9/1)
Arts 10 00060 i187
1 (1/2)
Arts 10 00060 i188
3 (5/2)
Arts 10 00060 i189Clematis L.NCS S 2040-R60BNCS S 1510-R40BNCS S 2030-G50YNCS S 3010-G90Y
Arts 10 00060 i190
3 (7/1)
Arts 10 00060 i191
1 (1/2)
Arts 10 00060 i192
10 (25/7)
Arts 10 00060 i193
3 (5/2)
NCS S 2030-G50YNCS S 3040-R50BNCS S 6020-R30BNCS S 6010-Y50R
Arts 10 00060 i194
10 (25/7)
Arts 10 00060 i195
1 (4/1)
Arts 10 00060 i196
1 (1/1)
Arts 10 00060 i197
2 (4/2)
Arts 10 00060 i198Syringa vulgaris L.NCS S 1510-R60BNCS S 1050-G20YNCS S 3030-G40YNCS S 2010-G50Y
Arts 10 00060 i199
1 (1/1)
Arts 10 00060 i200
11 (22/1)
Arts 10 00060 i201
8 (9/1)
Arts 10 00060 i202
3 (15/12)
NCS S 2040-R60BNCS S 2030-G50YNCS S 2020-Y10RNCS S 3010-Y50R
Arts 10 00060 i203
3 (7/1)
Arts 10 00060 i204
10 (25/7)
Arts 10 00060 i205
3 (7/3)
Arts 10 00060 i206
1 (1/1)
Arts 10 00060 i207Cornus alba L.NCS S 0500NNCS S 3030-G40YNCS S 1005-G90YNCS S 2570R
Arts 10 00060 i208
1 (1/4)
Arts 10 00060 i209
8 (9/1)
Arts 10 00060 i210
3 (5/5)
Arts 10 00060 i211
2 (5/2)
NCS S 2570-Y80RNCS S 3050-G40YNCS S 5030-Y80RNCS S 2570-Y90R
Arts 10 00060 i212
1 (3/2)
Arts 10 00060 i213
4 (11/1)
Arts 10 00060 i214
3 (3/3)
Arts 10 00060 i215
1 (7/5)
Arts 10 00060 i216Magnolia kobus DC.NCS S 0502RNCS S 1050-G20YNCS S 1020-Y20RNCS S 3010-G30Y
Arts 10 00060 i217
2 (3/2)
Arts 10 00060 i218
11 (22/1)
Arts 10 00060 i219
1 (1/7)
Arts 10 00060 i220
3 (4/2)
NCS S 0530-Y80RNCS S 0510-G50YNCS S 2030-Y20RNCS S 3010-G90Y
Arts 10 00060 i221
3 (6/4)
Arts 10 00060 i222
2 (3/1)
Arts 10 00060 i223
1 (2/8)
Arts 10 00060 i224
3 (5/2)
Arts 10 00060 i225Hydrangea arborescens L.NCS S 2030-G50YNCS S 0502-Y50RNCS S 1015-Y50RNCS S 6010-Y50R
Arts 10 00060 i226
10 (25/7)
Arts 10 00060 i227
1 (1/10)
Arts 10 00060 i228
1 (1/6)
Arts 10 00060 i229
2 (4/2)
NCS S 1050-G20YNCS S 0530-Y80RNCS S 0550-Y80RNCS S 5030-Y80R
Arts 10 00060 i230
11 (22/1)
Arts 10 00060 i231
3 (6/4)
Arts 10 00060 i232
2 (2/2)
Arts 10 00060 i233
3 (3/3)
Arts 10 00060 i234Hydrangea macrophylla L.NCS S 2030-G50YNCS S 1040B NCS S 1040-R90BNCS S 5030-Y80R
Arts 10 00060 i235
10 (25/7)
Arts 10 00060 i236
1 (2/3)
Arts 10 00060 i237
1 (2/1)
Arts 10 00060 i238
3 (3/3)
NCS S 1050-G20YNCS S 1030-R80BNCS S 2040-R60BNCS S 7020-R20B
Arts 10 00060 i239
11 (22/1)
Arts 10 00060 i240
1 (2/1)
Arts 10 00060 i241
3 (7/1)
Arts 10 00060 i242
1 (1/1)
Arts 10 00060 i243Hydrangea arborescens L.NCS S 2030-G50YNCS S 0502RNCS S 0550-Y80RNCS S 3030-Y70R
Arts 10 00060 i244
10 (25/7)
Arts 10 00060 i245
2 (3/2)
Arts 10 00060 i246
2 (2/2)
Arts 10 00060 i247
1 (1/6)
NCS S 1050-G20YNCS S 1030-R30BNCS S 1580-Y90RNCS S 2570R
Arts 10 00060 i248
11 (22/1)
Arts 10 00060 i249
1 (4/1)
Arts 10 00060 i250
1 (7/2)
Arts 10 00060 i251
2 (5/2)
Table A3. One hundred and twenty-three color samples taken from the blooming plants identified in the research area. The numbers below the color sample provide the information how many times a given color appears in the table (how many times it appears in all natural samples/how many times it appears in the analyzed architectural objects).
Table A3. One hundred and twenty-three color samples taken from the blooming plants identified in the research area. The numbers below the color sample provide the information how many times a given color appears in the table (how many times it appears in all natural samples/how many times it appears in the analyzed architectural objects).
ImageNameSpringSummerAutumn
Arts 10 00060 i252Helianthus L.NCS S 2030-G50YNCS S 0550Y NCS S 0540-Y20R
Arts 10 00060 i253
9 (25/7)
Arts 10 00060 i254
4 (10/2)
Arts 10 00060 i255
6 (6/2)
NCS S 2060-G50Y NCS S 3040-G40Y NCS S 6010-Y50R
Arts 10 00060 i256
6 (14/1)
Arts 10 00060 i257
12 (16/2)
Arts 10 00060 i258
1 (4/2)
Arts 10 00060 i259Kniphofia uvaria (L.) OkenNCS S 2010-G50YNCS S 0550YNCS S 2020-Y10R
Arts 10 00060 i260
7 (15/12)
Arts 10 00060 i261
4 (10/2)
Arts 10 00060 i262
3 (7/3)
NCS S 2030-G50YNCS S 0550-Y60RNCS S 0570-Y60R
Arts 10 00060 i263
9 (25/7)
Arts 10 00060 i264
3 (4/8)
Arts 10 00060 i265
2 (3/1)
Arts 10 00060 i266Chrysanthemum coreanum H. Lev. et VaniotNCS S 2030-G50YNCS S 0540YNCS S 0550Y
Arts 10 00060 i267
9 (25/7)
Arts 10 00060 i268
7 (9/3)
Arts 10 00060 i269
4 (10/2)
NCS S 3010-G30YNCS S 3050-G40YNCS S 0570-Y60R
Arts 10 00060 i270
1 (4/2)
Arts 10 00060 i271
4 (11/1)
Arts 10 00060 i272
2 (3/1)
Arts 10 00060 i273Verbena hybryda L.NCS S 2060-G50YNCS S 1050-G20YNCS S 2010-G50Y
Arts 10 00060 i274
6 (14/1)
Arts 10 00060 i275
11 (22/1)
Arts 10 00060 i276
7 (15/12)
NCS S 1580-Y90RNCS S 1580-Y90RNCS S 2570-Y90R
Arts 10 00060 i277
5 (7/2)
Arts 10 00060 i278
5 (7/2)
Arts 10 00060 i279
3 (7/5)
Arts 10 00060 i280Verbena hybryda L.NCS S 0300NNCS S 0300NNCS S 0505Y
Arts 10 00060 i281
2 (4/4)
Arts 10 00060 i282
2 (4/4)
Arts 10 00060 i283
1 (1/1)
NCS S 2030-G50YNCS S 1050-G20Y NCS S 2010-G50Y
Arts 10 00060 i284
9 (25/7)
Arts 10 00060 i285
11 (22/1)
Arts 10 00060 i286
7 (15/12)
Arts 10 00060 i287Iris germanica L.NCS S 2030-G50YNCS S 1015-Y30RNCS S 0540Y
Arts 10 00060 i288
9 (25/7)
Arts 10 00060 i289
1 (2/7)
Arts 10 00060 i290
7 (9/3)
NCS S 1050-G20YNCS S 3040-R50BNCS S 3040-G40Y
Arts 10 00060 i291
11 (22/1)
Arts 10 00060 i292
3 (4/1)
Arts 10 00060 i293
12 (16/2)
Arts 10 00060 i294Lilium martagon L.NCS S 2030-G50YNCS S 1030-Y30RNCS S 0540Y
Arts 10 00060 i295
9 (25/7)
Arts 10 00060 i296
3 (3/2)
Arts 10 00060 i297
7 (9/3)
NCS S 2060-G50YNCS S 0530-Y80RNCS S 3040-G40Y
Arts 10 00060 i298
6 (14/1)
Arts 10 00060 i299
3 (6/4)
Arts 10 00060 i300
12 (16/2)
Arts 10 00060 i301Lilium bulbiferum L.NCS S 2030-G50YNCS S 0540-Y20RNCS S 0540Y
Arts 10 00060 i302
9 (25/7)
Arts 10 00060 i303
6 (6/2)
Arts 10 00060 i304
7 (9/3)
NCS S 2060-G50YNCS S 0550-Y60RNCS S 3040-G40Y
Arts 10 00060 i305
6 (14/1)
Arts 10 00060 i306
3 (4/8)
Arts 10 00060 i307
12 (16/2)
Arts 10 00060 i308Lilium L.NCS S 1050-G20YNCS S 2570-Y70RNCS S 0540Y
Arts 10 00060 i309
11 (22/1)
Arts 10 00060 i310
1 (1/1)
Arts 10 00060 i311
7 (9/3)
NCS S 4030-B70GNCS S 2570-Y90RNCS S 2020-Y10R
Arts 10 00060 i312
3 (5/1)
Arts 10 00060 i313
3 (7/5)
Arts 10 00060 i314
3 (7/3)
Arts 10 00060 i315Lilium L.NCS S 1050-G20YNCS S 1580-Y90RNCS S 0540-Y20R
Arts 10 00060 i316
11 (22/1)
Arts 10 00060 i317
5 (7/2)
Arts 10 00060 i318
6 (6/2)
NCS S 4030-B70GNCS S 2570-Y90RNCS S 0540Y
Arts 10 00060 i319
3 (5/1)
Arts 10 00060 i320
3 (7/5)
Arts 10 00060 i321
7 (9/3)
Arts 10 00060 i322Lilium L.NCS S 1050-G20YNCS S 0550YNCS S 1030-Y30R
Arts 10 00060 i323
11 (22/1)
Arts 10 00060 i324
4 (10/2)
Arts 10 00060 i325
3 (3/2)
NCS S 3030-G40YNCS S 0650-Y60RNCS S 3040-G40Y
Arts 10 00060 i326
1 (9/1)
Arts 10 00060 i327
1 (1/3)
Arts 10 00060 i328
12 (16/2)
Arts 10 00060 i329Rosa L.NCS S 2060-G50YNCS S 0530-Y80RNCS S 0530Y
Arts 10 00060 i330
6 (14/1)
Arts 10 00060 i331
3 (6/4)
Arts 10 00060 i332
2 (3/5)
NCS S 3040-G40YNCS S 0550-Y60RNCS S 0540-Y20R
Arts 10 00060 i333
12 (16/2)
Arts 10 00060 i334
3 (4/8)
Arts 10 00060 i335
6 (6/2)
Arts 10 00060 i336Rosa L.NCS S 1050-G20YNCS S 1030-R30BNCS S 0530-Y80R
Arts 10 00060 i337
11 (22/1)
Arts 10 00060 i338
2 (4/1)
Arts 10 00060 i339
3 (6/4)
NCS S 3040-G40YNCS S 0560-Y80RNCS S 0540-Y20R
Arts 10 00060 i340
12 (16/2)
Arts 10 00060 i341
2 (2/1)
Arts 10 00060 i342
6 (6/2)
Arts 10 00060 i343Rosa L.NCS S 1050-G20YNCS S 1580-Y90RNCS S 0540-Y20R
Arts 10 00060 i344
11 (22/1)
Arts 10 00060 i345
5 (7/2)
Arts 10 00060 i346
6 (6/2)
NCS S 2060-G50YNCS S 2570-Y80RNCS S 2570-Y80R
Arts 10 00060 i347
6 (14/1)
Arts 10 00060 i348
2 (3/2)
Arts 10 00060 i349
2 (3/2)
Arts 10 00060 i350Paeonia lactiflora L.NCS S 1050-G20YNCS S 0530YNCS S 3040-G40Y
Arts 10 00060 i351
11 (22/1)
Arts 10 00060 i352
2 (3/5)
Arts 10 00060 i353
12 (16/2)
NCS S 3050-G40YNCS S 1580-Y90RNCS S 1030-Y30R
Arts 10 00060 i354
4 (11/1)
Arts 10 00060 i355
5 (7/2)
Arts 10 00060 i356
3 (3/2)
Arts 10 00060 i357Digitalis purpurea L.NCS S 2030-G50YNCS S 1030-R30BNCS S 3040-G40Y
Arts 10 00060 i358
9 (25/7)
Arts 10 00060 i359
2 (4/1)
Arts 10 00060 i360
12 (16/2)
NCS S 3050-G40YNCS S 3040-R50BNCS S 2010-G50Y
Arts 10 00060 i361
4 (11/1)
Arts 10 00060 i362
3 (4/1)
Arts 10 00060 i363
7 (15/12)
Arts 10 00060 i364Lobelia L.NCS S 3040-G40YNCS S 0155-R80BNCS S 1040B
Arts 10 00060 i365
12 (16/2)
Arts 10 00060 i366
2 (2/1)
Arts 10 00060 i367
1 (2/3)
NCS S 3050-G40YNCS S 2040-R60BNCS S 2010-G50Y
Arts 10 00060 i368
4 (11/1)
Arts 10 00060 i369
4 (7/1)
Arts 10 00060 i370
7 (15/12)
Arts 10 00060 i371Viola tricolor L.NCS S 1050-G20YNCS S 0540YNCS S 2020-Y10R
Arts 10 00060 i372
11 (22/1)
Arts 10 00060 i373
7 (9/3)
Arts 10 00060 i374
3 (7/3)
NCS S 3040-R50BNCS S 2040-R60BNCS S 3030-R60B
Arts 10 00060 i375
3 (4/1)
Arts 10 00060 i376
4 (7/1)
Arts 10 00060 i377
2 (2/1)
Arts 10 00060 i378Centaurea cyanus L.NCS S 3040-G40YNCS S 1040-R90BNCS S 3040-G40Y
Arts 10 00060 i379
12 (16/2)
Arts 10 00060 i380
1 (2/1)
Arts 10 00060 i381
12 (16/2)
NCS S 4030-B70GNCS S 0155-R80BNCS S 2010-G50Y
Arts 10 00060 i382
3 (5/1)
Arts 10 00060 i383
2 (2/1)
Arts 10 00060 i384
7 (15/12)
Arts 10 00060 i385Myosotis L.NCS S 1030-B10GNCS S 1030-R80BNCS S 2030-G50Y
Arts 10 00060 i386
1 (1/2)
Arts 10 00060 i387
1 (2/1)
Arts 10 00060 i388
9 (25/7)
Arts 10 00060 i389Lavandula L.NCS S 1050-G20YNCS S 3030-R60BNCS S 3005-R60B
Arts 10 00060 i390
11 (22/1)
Arts 10 00060 i391
2 (2/1)
Arts 10 00060 i392
1 (1/2)
NCS S 2040-R60BNCS S 2040-R60BNCS S 2010-G50Y
Arts 10 00060 i393
4 (7/1)
Arts 10 00060 i394
4 (7/1)
Arts 10 00060 i395
7 (15/12)
Table A4. The colors of the exterior façades of the examined buildings designed by Victor Horta.
Table A4. The colors of the exterior façades of the examined buildings designed by Victor Horta.
ImageNameNatural LightElectric Light
Arts 10 00060 i396Tassel House façade during the day, the general viewNSC S 1002-Y50R NCS S 1005-Y40R
Arts 10 00060 i397
4
Arts 10 00060 i398
5
NCS S 1005-G90YNCS S 2010-G50Y
Arts 10 00060 i399
2
Arts 10 00060 i400
3
Arts 10 00060 i401Tassel House façade in the evening, illuminated from the inside NCS S 2020-Y10RNCS S 3010-Y50R
Arts 10 00060 i402
1
Arts 10 00060 i403
1
NCS S 3010-G30YNCS S 5030-Y80R
Arts 10 00060 i404
2
Arts 10 00060 i405
3
Arts 10 00060 i406Tassel House, the entrance area during the dayNCS S 0500NNCS S 1005-G90Y
Arts 10 00060 i407
4
Arts 10 00060 i408
2
NCS S 2005-R80BNCS S 4030-Y50R
Arts 10 00060 i409
3
Arts 10 00060 i410
3
Arts 10 00060 i411Tassel House, the entrance area during in the evening NCS S 1005-Y40RNSC S 1510-Y60R
Arts 10 00060 i412
5
Arts 10 00060 i413
2
NCS S 3005-R60BNCS S 5030-Y80R
Arts 10 00060 i414
2
Arts 10 00060 i415
3
Arts 10 00060 i416Tassel House, the window on the third floorNCS S 1002-Y50RNCS S 2010-G50Y
Arts 10 00060 i417
4
Arts 10 00060 i418
3
Arts 10 00060 i419Tassel House, the window on the second floorNSC S 1002-Y50RNCS S 2010-G50Y
Arts 10 00060 i420
4
Arts 10 00060 i421
3
Arts 10 00060 i422Tassel House, windows illuminated from inside NCS S 3005-R60BNCS S 3010-G30Y
Arts 10 00060 i423
2
Arts 10 00060 i424
2
NCS S 3005-Y50RNSC S 1510-Y60R
Arts 10 00060 i425
1
Arts 10 00060 i426
2
Arts 10 00060 i427Horta House and Studio, the view of both facades NCS S 0500NNCS S 1000N
Arts 10 00060 i428
4
Arts 10 00060 i429
5
NCS S 1005-Y40RNCS S 4030-Y50R
Arts 10 00060 i430
5
Arts 10 00060 i431
3
Arts 10 00060 i432Horta Studio, the window on the first floorNCS S 2030-Y20R NCS S 5030-Y80R
Arts 10 00060 i433
4
Arts 10 00060 i434
3
Arts 10 00060 i435Horta House, the entrance areaNCS S 0500NNCS S 2005-R80BNCS S 2010-B30G
Arts 10 00060 i436
4
Arts 10 00060 i437
3
Arts 10 00060 i438
1
NCS S 2030-Y20RNCS S 4030-Y50RNCS S 1020-Y20R
Arts 10 00060 i439
4
Arts 10 00060 i440
3
Arts 10 00060 i441
3
Arts 10 00060 i442Horta House, A balcony above the entranceNCS S 1005-Y40RNCS S 1000N
Arts 10 00060 i443
5
Arts 10 00060 i444
5
NCS S 1020-Y20RNCS S 2030-Y20R
Arts 10 00060 i445
3
Arts 10 00060 i446
4
Arts 10 00060 i447Horta House, The entrance areaNSC S 1002-Y50RNCS S 1000N
Arts 10 00060 i448
4
Arts 10 00060 i449
5
NCS S 2030-Y20RNCS S 8005-Y80R
Arts 10 00060 i450
4
Arts 10 00060 i451
1
Arts 10 00060 i452 NCS S 1005-Y40RNCS S 1000N
Arts 10 00060 i453
5
Arts 10 00060 i454
5
Arts 10 00060 i455Horta House, A glass floor of a balconyNCS S 0500NNCS S 1000N
Arts 10 00060 i456
4
Arts 10 00060 i457
5
NCS S 2005-R80BNCS S 1020-Y20R
Arts 10 00060 i458
3
Arts 10 00060 i459
3
Table A5. The colors of the interiors of the examined buildings designed by Victor Horta.
Table A5. The colors of the interiors of the examined buildings designed by Victor Horta.
ImageNameNatural LightElectric Light
Arts 10 00060 i460Tassel House the decorative staircaseNCS S 1015YNCS S 1015-Y30RNSC S 1030-Y40RNCS S 0550-Y60R
Arts 10 00060 i461
6
Arts 10 00060 i462
7
Arts 10 00060 i463
3
Arts 10 00060 i464
8
NCS S 0502YNCS S 2570RNCS S 4030-Y50RNCS S 2570-Y90R
Arts 10 00060 i465
11
Arts 10 00060 i466
2
Arts 10 00060 i467
6
Arts 10 00060 i468
5
Arts 10 00060 i469Tassel House the entrance areaNCS S 0300NNCS S 1015YNCS S 0505-Y10RNSC S 1030-Y40R
Arts 10 00060 i470
4
Arts 10 00060 i471
6
Arts 10 00060 i472
3
Arts 10 00060 i473
3
NCS S 0502YNCS S 2570RNCS S 0502-Y50RNCS S 2570-Y90R
Arts 10 00060 i474
11
Arts 10 00060 i475
2
Arts 10 00060 i476
10
Arts 10 00060 i477
5
Arts 10 00060 i478Tassel house, the decorative staircaseNCS S 0502YNCS S 1015-Y30RNCS S 0505YNCS S 0550-Y60R
Arts 10 00060 i479
11
Arts 10 00060 i480
7
Arts 10 00060 i481
1
Arts 10 00060 i482
8
NCS S 0502-Y50RNCS S 1005-G90YNCS S 0502RNCS S 2010-G50Y
Arts 10 00060 i483
10
Arts 10 00060 i484
3
Arts 10 00060 i485
2
Arts 10 00060 i486
9
Arts 10 00060 i487Tassel house, the waiting area on the ground floorNCS S 0300NNCS S 0540YNCS S 0505-Y10RNCS S 0550Y
Arts 10 00060 i488
4
Arts 10 00060 i489
3
Arts 10 00060 i490
3
Arts 10 00060 i491
2
NCS S 0550-Y80RNCS S 4030-B30GNCS S 0570-Y60RNCS S 4030-B70G
Arts 10 00060 i492
2
Arts 10 00060 i493
2
Arts 10 00060 i494
1
Arts 10 00060 i495
1
Arts 10 00060 i496Tassel House, the stained-glass window on the second floorNCS S 0530YNCS S 1030-R30BNCS S 2030-G50YNCS S 0530-Y80R
Arts 10 00060 i497
5
Arts 10 00060 i498
1
Arts 10 00060 i499
7
Arts 10 00060 i500
4
NCS S 1030-B10GNCS S 0155-R80BNCS S 1040BNCS S 4030-B30G
Arts 10 00060 i501
2
Arts 10 00060 i502
1
Arts 10 00060 i503
3
Arts 10 00060 i504
2
NCS S 2040-R60BNCS S 1050-G20YNCS S 3040-R50BNCS S 3050-G40Y
Arts 10 00060 i505
1
Arts 10 00060 i506
1
Arts 10 00060 i507
1
Arts 10 00060 i508
1
Arts 10 00060 i509Tassel House, the second floor in the daylightNCS S 0502YNCS S 1015YNCS S 2030-G50YNCS S 2060-G50Y
Arts 10 00060 i510
11
Arts 10 00060 i511
6
Arts 10 00060 i512
7
Arts 10 00060 i513
1
NCS S 1015-Y30RNCS S 7500NNCS S 3040-G40YNCS S 1040B
Arts 10 00060 i514
7
Arts 10 00060 i515
2
Arts 10 00060 i516
2
Arts 10 00060 i517
3
Arts 10 00060 i518Tassel House, the second floor in the artificial light NCS S 1015-Y30RNSC S 1030-Y40R
Arts 10 00060 i519
7
Arts 10 00060 i520
3
NCS S 3010-G90YNCS S 2570-Y90R
Arts 10 00060 i521
2
Arts 10 00060 i522
5
Arts 10 00060 i523Tassel House, the second floor in the daylightNCS S 0502YNCS S 1015-Y50RNCS S 1020-Y20R
Arts 10 00060 i524
11
Arts 10 00060 i525
6
Arts 10 00060 i526
4
NCS S 2010-G50YNCS S 4030-Y50RNCS S 2020-B90G
Arts 10 00060 i527
9
Arts 10 00060 i528
6
Arts 10 00060 i529
1
Arts 10 00060 i530Tassel House, the stained-glass windowNCS S 0540YNCS S 3030-R60BNCS S 3040-Y40R
Arts 10 00060 i531
3
Arts 10 00060 i532
1
Arts 10 00060 i533
1
Arts 10 00060 i534Tassel House, the mosaic on the ground floorNCS S 0502YNCS S 0550-Y60RNCS S 0502-Y50RNCS S 0650-Y60R
Arts 10 00060 i535
11
Arts 10 00060 i536
8
Arts 10 00060 i537
10
Arts 10 00060 i538
3
NCS S 1580-Y90RNCS S 6010-Y50RNCS S 2570-Y80RNCS S 7010-Y40R
Arts 10 00060 i539
2
Arts 10 00060 i540
2
Arts 10 00060 i541
2
Arts 10 00060 i542
2
Arts 10 00060 i543Tassel House, the octagonal vestibule with the skylightNCS S 0502YNCS S 0540YNCS S 0502-Y50RNCS S 0550Y
Arts 10 00060 i544
11
Arts 10 00060 i545
3
Arts 10 00060 i546
10
Arts 10 00060 i547
2
NCS S 2010-G50YNCS S 0550-Y60RNCS S 3010-G90YNCS S 0650-Y60R
Arts 10 00060 i548
9
Arts 10 00060 i549
8
Arts 10 00060 i550
2
Arts 10 00060 i551
3
Arts 10 00060 i552Tassel House, the stained-glass windows in the octagonal vestibule NCS S 0530YNCS S 2010-G50YNCS S 0540-Y20RNCS S 2020-Y10R
Arts 10 00060 i553
5
Arts 10 00060 i554
9
Arts 10 00060 i555
2
Arts 10 00060 i556
3
NCS S 1510-R60BNCS S 6020-R30BNCS S 1510-R40BNCS S 7020-R20B
Arts 10 00060 i557
1
Arts 10 00060 i558
1
Arts 10 00060 i559
2
Arts 10 00060 i560
1
Arts 10 00060 i561Tassel House, the octagonal vestibule on the ground floorNCS S 0530YNCS S 0550-Y60RNCS S 0540-Y20RNCS S 0650-Y60R
Arts 10 00060 i562
5
Arts 10 00060 i563
8
Arts 10 00060 i564
2
Arts 10 00060 i565
3
NCS S 2010-G50YNCS S 1580-Y90RNCS S 2020-Y10RNCS S 2570-Y80R
Arts 10 00060 i566
9
Arts 10 00060 i567
2
Arts 10 00060 i568
3
Arts 10 00060 i569
2
Arts 10 00060 i570Tassel House, the wardrobe in the entrance zoneNCS S 0502YNCS S 2010-G50YNCS S 0502-Y50RNCS S 2020-Y10R
Arts 10 00060 i571
11
Arts 10 00060 i572
9
Arts 10 00060 i573
10
Arts 10 00060 i574
3
NCS S 7005-Y80RNCS S 6010-Y50RNCS S 7500NNCS S 7010-Y40R
Arts 10 00060 i575
1
Arts 10 00060 i576
2
Arts 10 00060 i577
2
Arts 10 00060 i578
2
Arts 10 00060 i579Tassel House, the dining room on the ground floorNCS S 1015-Y30RNCS S 3030-Y70RNCS S 0550-Y60RNCS S 2570-Y90R
Arts 10 00060 i580
7
Arts 10 00060 i581
6
Arts 10 00060 i582
8
Arts 10 00060 i583
5
Arts 10 00060 i584Horta House, the dining room and the family room on the ground floor NCS S 0502-Y50RNCS S 0530Y
Arts 10 00060 i585
10
Arts 10 00060 i586
5
NCS S 0550-Y60RNCS S 2570-Y90R
Arts 10 00060 i587
8
Arts 10 00060 i588
5
Arts 10 00060 i589Horta House, the dining room and the family room on the ground floor in the daylightNCS S 0502YNCS S 0515-Y30R
Arts 10 00060 i590
11
Arts 10 00060 i591
2
NCS S 1005-G90YNCS S 3030-Y70R
Arts 10 00060 i592
3
Arts 10 00060 i593
6
Arts 10 00060 i594Horta House, the dining room and the family room on the ground floor in the electric light NCS S 0502-Y50RNCS S 1015-Y30R
Arts 10 00060 i595
10
Arts 10 00060 i596
7
NCS S 1060-Y70RNCS S 4030-Y50R
Arts 10 00060 i597
2
Arts 10 00060 i598
6
Arts 10 00060 i599Horta House, the family room on the ground floorNCS S 0502YNCS S 0515-Y30RNCS S 0502-Y50RNCS S 1015-Y30R
Arts 10 00060 i600
11
Arts 10 00060 i601
2
Arts 10 00060 i602
10
Arts 10 00060 i603
7
NCS S 0540-Y60RNCS S 2030-G50YNCS S 1060-Y70RNCS S 4030-Y50R
Arts 10 00060 i604
1
Arts 10 00060 i605
6
Arts 10 00060 i606
2
Arts 10 00060 i607
6
Arts 10 00060 i608Horta House, the porte fenêtre to the gardenNCS S 0502YNCS S 0530-Y80RNCS S 2030-G80Y
Arts 10 00060 i609
11
Arts 10 00060 i610
4
Arts 10 00060 i611
1
NCS S 0550-Y60RNCS S 4030-Y50RNCS S 3030-G40Y
Arts 10 00060 i612
8
Arts 10 00060 i613
6
Arts 10 00060 i614
1
Arts 10 00060 i615Horta House, the stained-glass doorNCS S 1015YNCS S 0530-Y80RNCS S 0530YNCS S 0560-Y80R
Arts 10 00060 i616
6
Arts 10 00060 i617
4
Arts 10 00060 i618
5
Arts 10 00060 i619
1
NCS S 0502-Y50RNCS S 3030-Y70RNCS S 1005-Y40RNCS S 2570-Y70R
Arts 10 00060 i620
10
Arts 10 00060 i621
6
Arts 10 00060 i622
2
Arts 10 00060 i623
1
Arts 10 00060 i624Horta House, the dressing room on the first floorNCS S 1005-G90YNCS S 0510-G50YNCS S 1015YNCS S 2030-G50Y
Arts 10 00060 i625
3
Arts 10 00060 i626
1
Arts 10 00060 i627
6
Arts 10 00060 i628
6
NCS S 0502-Y50RNCS S 1020-Y20RNCS S 1005-Y40RNCS S 4030-Y50R
Arts 10 00060 i629
10
Arts 10 00060 i630
4
Arts 10 00060 i631
2
Arts 10 00060 i632
6
Arts 10 00060 i633Horta House, the decorative staircase NCS S 0505-Y10RNCS S 1015YNCS S 0502-G90YNCS S 1030-Y30R
Arts 10 00060 i634
3
Arts 10 00060 i635
6
Arts 10 00060 i636
4
Arts 10 00060 i637
2
NCS S 0505-Y40RNCS S 2030-Y20RNCS S 1015-Y50RNCS S 3030-Y70R
Arts 10 00060 i638
2
Arts 10 00060 i639
4
Arts 10 00060 i640
6
Arts 10 00060 i641
6
Arts 10 00060 i642Horta House, the fireplaceNCS S 2030-G50YNCS S 0550-Y80RNCS S 1015-Y50RNCS S 1030-Y30R
Arts 10 00060 i643
6
Arts 10 00060 i644
2
Arts 10 00060 i645
6
Arts 10 00060 i646
2
Arts 10 00060 i647Horta House, the stained-glass skylight above the main stairsNCS S 0300NNCS S 0502-G90YNCS S 2010-G50YNCS S 2030-G50Y
Arts 10 00060 i648
4
Arts 10 00060 i649
4
Arts 10 00060 i650
9
Arts 10 00060 i651
6
NCS S 0505-Y40RNCS S 1020-Y20RNCS S 1015-Y50RNCS S 3030-Y70R
Arts 10 00060 i652
2
Arts 10 00060 i653
4
Arts 10 00060 i654
6
Arts 10 00060 i655
6
Arts 10 00060 i656Horta House, the stained-glass skylight above the main stairsNCS S 0300NNCS S 1000NNCS S 0502-G90YNCS S 3040-G40Y
Arts 10 00060 i657
4
Arts 10 00060 i658
2
Arts 10 00060 i659
4
Arts 10 00060 i660
2
Arts 10 00060 i661Horta House, the stained-glass skylight above the main stairsNCS S 1000NNCS S 0502-G90YNCS S 2010-G50YNCS S 2030-Y20R
Arts 10 00060 i662
2
Arts 10 00060 i663
4
Arts 10 00060 i664
9
Arts 10 00060 i665
4
Arts 10 00060 i666Horta House, the daughter’s roomNCS S 1040-R90BNCS S 1020-Y20RNCS S 1040BNCS S 2030-Y20R
Arts 10 00060 i667
1
Arts 10 00060 i668
4
Arts 10 00060 i669
3
Arts 10 00060 i670
4
Arts 10 00060 i671Horta House, the daughter’s roomNCS S 1015-Y50RNCS S 1030-R80BNCS S 3030-Y70RNCS S 1030-B10G
Arts 10 00060 i672
6
Arts 10 00060 i673
1
Arts 10 00060 i674
6
Arts 10 00060 i675
2
Arts 10 00060 i676Horta House, the way from master bedroom to bathroomsNCS S 0530-Y80RNCS S 2030-G50YNCS S 1015-Y50RNCS S 2030-Y20R
Arts 10 00060 i677
4
Arts 10 00060 i678
6
Arts 10 00060 i679
6
Arts 10 00060 i680
4
Arts 10 00060 i681Horta House, the boudoir NCS S 0502RNCS S 2010-G50YNCS S 1510-R40BNCS S 5030-Y80R
Arts 10 00060 i682
2
Arts 10 00060 i683
9
Arts 10 00060 i684
2
Arts 10 00060 i685
1

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Figure 1. The façade of the Tassel House designed by Victor Horta.
Figure 1. The façade of the Tassel House designed by Victor Horta.
Arts 10 00060 g001
Figure 2. The biomorphic columns in the Tassel House façade.
Figure 2. The biomorphic columns in the Tassel House façade.
Arts 10 00060 g002
Figure 3. The façade of the Horta House and Studio (Maison et Atelier Horta).
Figure 3. The façade of the Horta House and Studio (Maison et Atelier Horta).
Arts 10 00060 g003
Figure 4. The bright interiors of the Horta House.
Figure 4. The bright interiors of the Horta House.
Arts 10 00060 g004
Figure 5. In the Tassel House, a large amount of daylight and biomorphic forms of structures and decorations clearly indicate the inspirations drawn from nature: (a) The skylight above the staircase; (b) the biological decoration and structure of the staircase.
Figure 5. In the Tassel House, a large amount of daylight and biomorphic forms of structures and decorations clearly indicate the inspirations drawn from nature: (a) The skylight above the staircase; (b) the biological decoration and structure of the staircase.
Arts 10 00060 g005
Figure 6. The effect of verticalism and biomorphic interior design observed in the Horta House.
Figure 6. The effect of verticalism and biomorphic interior design observed in the Horta House.
Arts 10 00060 g006
Figure 7. The colors of the Tassel House façade: (a) The Tassel House façade; (b) the Savonnières Stone ©ROCAMAT; (c) the Euville Stone ©ROCAMAT; (d) the Ritz Bleu Stone ©ROCAMAT.
Figure 7. The colors of the Tassel House façade: (a) The Tassel House façade; (b) the Savonnières Stone ©ROCAMAT; (c) the Euville Stone ©ROCAMAT; (d) the Ritz Bleu Stone ©ROCAMAT.
Arts 10 00060 g007
Figure 8. The natural colors and biomorphic motives of the stained-glass window on the first floor in the Tassel House.
Figure 8. The natural colors and biomorphic motives of the stained-glass window on the first floor in the Tassel House.
Arts 10 00060 g008
Figure 9. The green color used in the façade of the Tassel House is observed in the painted iron elements: Lintels, narrow vertical posts and a balustrade of the balcony on the second floor.
Figure 9. The green color used in the façade of the Tassel House is observed in the painted iron elements: Lintels, narrow vertical posts and a balustrade of the balcony on the second floor.
Arts 10 00060 g009
Figure 10. The natural colors and biomorphic structural forms in the Horta House: (a) The balcony; (b) the skylight.
Figure 10. The natural colors and biomorphic structural forms in the Horta House: (a) The balcony; (b) the skylight.
Arts 10 00060 g010
Table 1. The comparison of the occurrence of colors in the nature and the architecture of the examined buildings.
Table 1. The comparison of the occurrence of colors in the nature and the architecture of the examined buildings.
Predominant Colors Identified through the Research
in the Natural Environment
and in Architecture
Occurrence in Nature Based on 307 Samples/82 Colors Occurrence
in Architecture
Based on 251 Samples/81 Colors
Exteriors
(50 Samples)
Interiors
(201 Samples)
GROUP OF COLORS: GREEN (NATURE/ARCHITECTURE)
NCS S 2030-G50YNCS S 1050-G20YNCS S 3040-G40Y135 samples
43.97%
of all color samplesfrom nature
7 samples
14% of samples from exteriors
2.79%
of all color samplesfrom architecture
32 samples
15.92%
of samples from interiors
12.75%
of all color samples
from architecture
Arts 10 00060 i001 Arts 10 00060 i002 Arts 10 00060 i003
25/722/116/2
NCS S 2010-G50YNCS S 2060-G50YNCS S 3050-G40Y
Arts 10 00060 i004 Arts 10 00060 i005 Arts 10 00060 i006
15/1214/111/1
NCS S 1005-G90Y NCS S 3030-G40Y NCS S 3010-G30Y
Arts 10 00060 i007 Arts 10 00060 i008 Arts 10 00060 i009
5/5 9/14/2
GROUP OF COLORS: YELLOW
NCS S 0550YNCS S 0540YNCS S 2020-Y10R44 samples
14.3%
of all color samples from nature
7 samples
14%
of samples from exteriors
2.79%
of all the color samples from architecture
40 samples
19.9%
of samples from interiors
15.94%
of all the color samples from architecture
Arts 10 00060 i010 Arts 10 00060 i011 Arts 10 00060 i012
10/29/37/3
NCS S 2030-Y20RNCS S 1015YNCS S 1015-Y30R
Arts 10 00060 i013 Arts 10 00060 i014 Arts 10 00060 i015
2/83/62/7
NCS S 0540-Y20RNCS S 1020-Y20RNCS S 0530Y
Arts 10 00060 i016 Arts 10 00060 i017 Arts 10 00060 i018
6/21/73/5
GROUP OF COLORS: ORANGE
NCS S 0550-Y60RNCS S 1030-Y30R NCS S 0570-Y60R15 samples
4.89%
of all color samples from nature
0 samples22 samples
10.94%
of samples from interiors
7.97%
of all color samples from architecture
Arts 10 00060 i019 Arts 10 00060 i020 Arts 10 00060 i021
4/83/2 3/1
GROUP OF COLORS: RED
NCS S 2570-Y90RNCS S 1580-Y90RNCS S 2570R23 samples
7.5%
of all color samples from nature
0 samples12 samples
5.97%
of samples from interiors
4.78%
of all color samples from architecture
Arts 10 00060 i022 Arts 10 00060 i023 Arts 10 00060 i024
7/57/25/2
GROUP OF COLORS: PINK
NCS S 1005-Y40RNCS S 0530-Y80RNCS S 1015-Y50R21 samples
6.84%
of all color samples from nature
7 samples
14%
of samples from exteriors,
2.79%
of all color samples from architecture
18 samples
8.95%
of samples from interiors
7.17%
of all color samples from architecture
Arts 10 00060 i025 Arts 10 00060 i026 Arts 10 00060 i027
1/76/41/6
NCS S 0502RNCS S 1030-R30BNCS S 0550-Y80R
Arts 10 00060 i028 Arts 10 00060 i029 Arts 10 00060 i030
3/24/12/2
GROUP OF COLORS: WHITE & BEIGE
NCS S 0502YNCS S 0502-Y50R NCS S 0300N11 samples
3.58%
of all color samples from nature
13 samples
26%
of samples from exteriors,
5.19%
of all color samples from architecture
31 samples
15.42%
of samples from interiors,
12.35%
of all color samples from architecture
Arts 10 00060 i031 Arts 10 00060 i032 Arts 10 00060 i033
1/111/104/4
GROUP OF COLORS: VIOLET
NCS S 2040-R60BNCS S 3040-R50BNCS S 1510-R40B18 samples
5.86%
of all color samples from nature
2 samples
4%
of samples from exteriors,
0.8%
of all color samples from architecture
8 samples
3.98%
of samples from interiors,
3.19%
of all color samples from architecture
Arts 10 00060 i034 Arts 10 00060 i035 Arts 10 00060 i036
7/14/1 1/2
GROUP OF COLORS: BROWN
NCS S 4030-Y50RNCS S 6010-Y50RNCS S 5030-Y80R21 samples
6.84%
of all color samples from nature
9 samples
18%
of samples from exteriors,
3.59%
of all color samples from architecture
19 samples
9.45%
of samples from interiors,
7.57%
of all color samples from architecture
Arts 10 00060 i037 Arts 10 00060 i038 Arts 10 00060 i039
2/94/23/3
GROUP OF COLORS: BLUE
NCS S 1040B NCS S 1030-B10GNCS S 1030-R80B 12 samples
3.9%
of all color samples from nature
1 sample
2%
of samples from exteriors,
0.4%
of all color samples from architecture
11 samples
5.47%
of samples from interiors,
4.38%
of all color samples from architecture
Arts 10 00060 i040 Arts 10 00060 i041 Arts 10 00060 i042
2/32/12/1
GROUP OF COLORS: BLACK & GREY
NCS S 7500NNCS S 2005-R80B 2 samples
0.65%
of all color samples from nature
3 samples
6%
of samples from exteriors,
1.19%
of all color samples from architecture
2 samples
0.99%
of samples from interiors,
0.8%
of all color samples from architecture
Arts 10 00060 i043 Arts 10 00060 i044
1/21/3
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Widera, B. Colors Inspired by Nature Analyzed in Two Residential Buildings Designed by Victor Horta. Arts 2021, 10, 60. https://0-doi-org.brum.beds.ac.uk/10.3390/arts10030060

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Widera B. Colors Inspired by Nature Analyzed in Two Residential Buildings Designed by Victor Horta. Arts. 2021; 10(3):60. https://0-doi-org.brum.beds.ac.uk/10.3390/arts10030060

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Widera, Barbara. 2021. "Colors Inspired by Nature Analyzed in Two Residential Buildings Designed by Victor Horta" Arts 10, no. 3: 60. https://0-doi-org.brum.beds.ac.uk/10.3390/arts10030060

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