The Chemistry of Art and the Art of Chemistry - Journal of Chemical

Chemistry for Everyone

The Chemistry of Art and the Art of Chemistry

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C. Kafetzopoulos* Greek Pedagogical Institute, 36 Agiou Meletiou Street, Athens 112 57, Greece; *[email protected] N. Spyrellis Faculty of Chemical Engineering, National Technical University of Athens, Polytechneioupolis, Iroon Polytechneiou 9, 15780 Zografou, Athens, Greece A. Lymperopoulou-Karaliota Department of Chemistry, National and Kapodistrian University of Athens, 15771 Panepistimiopolis, Greece

From Pliny the Elder’s (23–79 C.E.) work, About the Greek Painting, testimonies about paints used in the past are known (1). Years later, in the Middle Ages, texts about pigments contained many chemical recipes. In his book Il Libro dell’ Arte (2), Cennino Cennini describes pencil making by mixing two parts lead and one part tin, the preparation of transparent paper by the application of linseed oil on paper, and the preparation of varnishes. He explains the preparation of many colors such as carbon black, terre-verte, bleu outremer, and others. Methods from early color chemistry and the preparation of pigments are found in Explanation of Painting (3), a book based on Byzantine and Italian techniques. Many reports from unpublished museum manuscripts included in the book Artists’ Pigments c. 1600–1835 indicate the importance of a background knowledge of chemistry in art and provide information on the preparation of colors (4). After the 19th century, an explosive production of new materials with applications in art followed the growth of chemistry (5). Nowadays innumerable materials and products of chemical industry are used by artists, such as paints, solvents, adhesives, papers, varnishes, and brushes. However, the contribution of chemistry to art is not widely known. The applications of chemistry in art and conservation of art works has resulted in various important products and techniques. For example, the chemical industry changed the materials used in the painter’s pallet. Artists use colors and nuances that their colleagues before the industrial revolution could not achieve or even imagine. The application of physicochemical methods of study, analysis, and conservation of art works as well as the application of scientific techniques in archaeology, which is called archaeometry, are very important (6). Despite the international scientific and technological growth in the past two decades, the overall interest in studying science appears to have decreased (7) and instructors are looking for motivating teaching methods. The concern for better chemical education is an international matter. One of the aims of the curriculum reformers has been to make science courses more relevant to the students. Attempts have been made to achieve this by relating art to chemistry in interdisciplinary, individualized, and consumer-oriented curricula (8). The relationship of chemistry with art, especially with painting, was presented in a collection of articles in this Journal (9). A short history of the chemistry of painting with information about pigments was presented by Friedstein (10). Chemists working in museums with conservators have succeeded in developing new techniques for the conservation of antiquities and art works (11). Chemistry and archaeology 1484

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have had a close relationship for the last two hundred years. During the 19th century, many eminent chemists, including Davy, Berzelius, Fresenius, and Faraday, published accounts of the analysis of archaeological materials. Today the contribution of chemistry to archaeology can be placed roughly into three categories: dating, conservation, and composition (12). The commonalities between science and fine arts can be epitomized in a few words: imagination, critical judgment, and esthetics (13). The approach of painting from a chemical point of view presents scientific and educational interest (14). Chemistry and art was the theme for the ACS-sponsored 2001 National Chemistry Week (NCW) with emphasis to the interdisciplinary connections (15). “In teaching science we need to remember that communication always benefits from imagination and esthetic sense” (16). A brief overview of the relationship of chemistry to the practice of art is found in several articles in this Journal (17). Chemistry at the interface of history, art, and archaeology is an interesting meld of disciplines that can help to solve old questions about archaeological articrafts and art works. Effective work in this area demands increasingly sophisticated equipment, increased knowledge of statistical software packages, increased interaction with members of related disciplines, and awareness of the literature of archaeometry, archaeology, and anthropology (18). The synthesis of Prussian blue and the conversion of raw umber to burnt umber (via loss of water of hydration) provides the basis for discussing topics like molecular formulas, molecular weight, and stoichiometry (19). In the article “Chemistry and Artists’ Colors, Part III” the syntheses for three pigments and their properties, and their classification are presented (20). The annotated bibliography of chemistry and art from past issues of the Journal of Chemical Education that tie in with the 2001 NCW theme is interesting. Searches in the JCE Index yielded nearly 300 articles related to chemistry and art, and the best of these of these are briefly described in the article by Jacobsen (21). The National Art Gallery of London and the Royal Society of Chemistry in England (RSC) have collaborated on a project, Chemistry and Art, that was aimed at students aged 11–18 years and their teachers. Some aspects of the techniques used in making five paintings are briefly discussed, together with something of their background and the chemistry involved in their making, deterioration, conservation, and restoration (22). Emphasis was given to laboratory safety rules. Dangers were pointed out and suitable precautions were taken.

Vol. 83 No. 10 October 2006

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At present chemistry suffers from a negative image problem. The inclusion of examples of the application of chemistry to art and archaeology in chemistry courses can help to give chemistry a positive image (23). Unfortunately, in the last decade, the term “chemical” has obtained a negative connotation because of the pollution from chemical industry products and the incorrect use of chemicals. An unexpected result is “chemophobia”, the absurd fear of chemicals and chemistry (24). Trying to reduce this fear of chemicals, in the present project, we mention products of chemical industry used in art, especially in painting. Students approach “the art of chemistry” through chemistry demonstrations in school and understand “the chemistry of art” preparing colors for painting via chemical reactions. To answer the question “what must be included in general chemistry?” we need to ask what fundamental ideas of chemistry are essential to modern chemistry. Chemical reactions are among them (25) and in the present project students learn about chemical changes through the products of chemical reactions and their applications in art. Art is used to make learning chemistry interesting and effective, as many chemistry instructors use games and puzzles to make learning chemistry more interesting (26). The present project (lecture and activity) was applied to an ordinary classroom and not to an integrated lecture–laboratory environment (27). It worked out properly and learning was effective as was indicated in the questionnaires, the students’ works, and, above all, their positive feelings after the development of the project. Methods The interdisciplinary and discovery-learning method is examined in this research. The laboratory leads to emotional learning and creates positive feelings by students toward their school. Participants in this project were 241 students, ages 14–15, from a junior high school in Athens, and six high school teachers. The lecture and the laboratory activity lasted one hour and a half. During a half-hour lecture, the students were informed about the production and use of colors in painting, topics of industrial, scientific, technological, and economic interest. Then the students prepared colored products as a result of simple chemical reactions of qualitative analysis (28) and observed the properties of these colored substances. They could use these colored substances to create simple watercolor paintings. The objective was for the students to investigate the connection between chemistry and art and realize the production of new materials as a contribution of chemistry to society. Before the actual teaching and the laboratory activities, a questionnaire was given to the students. It examined their knowledge about the connection between chemistry and art, especially with painting (see Figure 1, Questionnaire A). After the lecture and the laboratory activities, the students filled in their worksheet with certain chemical substances that give colored products (see Table 1 and the Supplemental MaterialW). Interesting painting samples were made during the project (see Figures 2 and 3). Finally, a second questionnaire was given to the students to test their knowledge on the applications of chemistry to art (see Figure 1, Questionnaire B). www.JCE.DivCHED.org

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The Project

The Lecture: The Chemistry of Art The lecture aimed to emphasize the relationship between chemistry and art. The following topics were discussed: • History of colors (5, 29) • Contribution of chemistry to the creation of new, highquality colors and the evolution of colors after the growth of chemistry the last 200 years (9, 14, 30) • Industrial production of colors (31) • Preparation of coloring substances in the school laboratory through simple chemical reactions (9, 14, 32)

There are many painting materials with special chemical interest like ink, pigments, inert materials, mediums, adhesives, coatings, varnishes, solvents, diluents, and tools. The chemistry of art is the chemistry behind these materials and mainly the chemistry of colorants. The term colorant embraces all color compounds, irrespective of their origin and utility for coloration or other purposes. They are organic or inorganic, natural or synthetic, but the last distinction is not generally meaningful, as some existing colorants originally had a natural source but are now produced synthetically. Pigments, which are often considered to be a subgroup of dyes, are practically insoluble in the media in which they are applied. Pigment particles have to be attached to substrates by additional substances functioning as adhesive. The substrate on which we paint can be wood, paper, plaster, metal, or a properly treated surface. The additional substance can be a polymer, oil, wax, egg, resin, and so forth. Paper is porous and can absorb color without the presence of an adhesive (as in the present project). Among these materials, we focus on inorganic pigments. Inorganic pigments were the first colors used in cave paintings. These were iron oxides, charcoal, and manganese dioxide. Years later, artificial pigments used by Egyptians were also in use by ancient Greeks. Most ancient Greek buildings were brightly colored, although monuments like the Acropolis no longer have their original colorful appearance (33). The artists were often working as chemists preparing colors, varnishes, solvents, and paintbrushes. Many colors prepared by the artists have been in use for thousands of years. Verdigris, known as green of Greeks (34), was prepared by the corrosion of copper. This was an important green as nature is very poor in green colors, except chlorophyll. The blue color ultramarine was made from a semi-precious stone, lapis lazuli, coming from the mines of Afghanistan. Its treatment was laborious, but the result was a marvellous color, which was very important for painters. For thousands of years chalk, calcium carbonate, was in use as a white color, but it is very weak and transparent. Lead white is one of the first synthetic pigments, which was made out of metallic lead and vinegar by ancient Greeks. White lead was the most important pigment used in painting but it is toxic and zinc white (1830) replaced it. White lead pigment discolors over time as PbS is formed, ZnO also forms ZnS over time, but ZnS is white, hence no discoloration. Titanium white (TiO2) is a superior white pigment compared to the other two, but it suffers from “chalking”—which the paint manufacturer claimed to be an advantage by calling it “self-cleaning” instead of the correct term, “chalking”. After 1920, titanium white was the white


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pigment used because it is cheap, nontoxic, and not transparent, giving it a very “strong” color with good covering ability. Prussian blue, which was prepared for the first time in 1704, replaced the expensive azurite and ultramarine. A number of blue colors with good properties were prepared as cobalt blue in 1802, and synthetic ultramarine was produced from inexpensive raw materials such as soda, clay, coal, and sulfur in 1828. In 1797 the metal chromium (the Greek word chroma means color) was discovered and could give many colors. Since 1820 many chromium colors have been prepared, such as chromium yellow and green oxide of chromium. The growth of chemistry made a significant change in the pallette of painters and brought a real revolution, with the composition of new products, innumerable new tints, new colors and dyes, both organic and inorganic. This is why we can speak about a chemical revolution of colors in the 19th century. During the Renaissance, artists were chemists and chemists were artists. The close relationship between art and chemistry is still obvious to the artist and to the chemist. This relationship provides a viable curriculum for an interdisciplinary approach to the teaching of chemistry (35). Today industrial companies prepare painting materials to give to modern painters. It is important to study the preparation and the properties of colors that we synthesize in the laboratory. It is important to study the chemistry of art.

The Laboratory Activity: The Art of Chemistry In the chemistry laboratory, we can study the properties of substances and produce substances with interesting physical and chemical properties. Using common reagents, we can prepare in the school laboratory colors that mainly are salts of transition metals (9, 15, 33). We can prepare blue, purple, brown, yellow, or green colors. These colors are substances usually insoluble in water, or colorful complex ions. These substances can be used in painting. Thus, we can prepare colors that painters before the 18th century could not even imagine to exist. The handling of these reagents needs knowledge of chemistry, attention, accuracy, and skill. This activity was named “the art of chemistry”. The initial idea of this laboratory activity is based on the qualitative analysis of cations and the characteristic colored products that lead to the identification of ions. The chemical substances used can be found in a common chemistry laboratory. The teachers worked with groups of 2 to 6 students. The materials given to each group of students were worksheets, reagents to make their own coloring substances, and sheets of paper and brushes to use their pigments. Students filled the worksheets (Table 1) using drops of reagents. Two drops from each solution of each row reacted with two drops from each solution of each column. Substances containing anions with interesting colored products are written in the horizontal row of a table in the worksheet (for example, potassium iodide KI, potassium hexacyanoferrate(II) K4[Fe(CN)6], sodium thiocyanate NaSCN). Substances containing cations used for preparation of colored products are written in the vertical column (for example, silver nitrate AgNO3, iron(III) chloride FeCl3, copper(II) sulfate CuSO4). Students were told to add drops of reagents and observe the products. About 50 mL of each solution in dropper bottles was enough for all students. 1486


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Table 1. Student's Worksheet NaCl

KBr

KI

Na2CO3 K4[Fe(CN)6] NaSCN

AgNO3 CoCl2 FeCl3 CuSO4 CuCl

Questionnaire A: Before the Lecture A1 Do you know if there is a relationship between chemistry and art and more specifically with painting? If your answer is YES, please give an example of the relationship between chemistry and art in the area of painting. A2 The contribution of chemistry to art especially to painting and restoration of works of art (paintings or stone monuments) is important. Can you name certain materials of chemical industry that are used in art? Questionnaire B. After the Lecture and the Laborator y Activities B1 After the laboratory activities, can you express the relationship of chemistry with painting? If your answer is YES, can you justify your answer? B2 The contribution of chemistry to the art especially to painting is important. Can you name materials of chemical industry that are used in painting or generally in art?

Figure 1. Questionnaires used before and after the activities.

The concentration of the water solutions of the reagents should be about 0.2 mol L᎑1. Examples of some characteristic colors prepared during the laboratory activities include: • Dark blue: solution of iron(III) chloride, FeCl3, and potassium hexacyanoferrate(II) K4[Fe(CN)6]. • Brown: solution of iron(III) chloride, FeCl3, and sodium thiocyanate, NaSCN. • Pink: solution of cobalt(II) chloride, CoCl2, and sodium carbonate, Na2CO3. • Green: solution of copper(I) chloride, CuCl, and sodium carbonate, Na2CO3.

Hazards Attention was given to the handling of all substances and the preparation of solutions. Many solutions contain cations of heavy metals, which are suspicious for health damage and toxicity. Instructions were given to the students not to touch substances or solutions. Students should wear goggles and


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gloves. Students neither handled solid substances, nor prepared solutions. All reagents were prepared by their teachers and were given to the students in 100-mL dropper bottles. Then, students using drops of each reagent on a sheet of paper observed the color change of the mixture. As an additional rule, the teacher can add the drops of each toxic reagent. If it is necessary, the teacher can handle reagents instead of his pupils to avoid incorrect use of chemicals. Microscale experiments are ideal for school activities because of safety, the small quantities of reagents used, and the small quantities of wastes produced. All litter was in a solid state, and was collected in plastic bags and removed. No liquid wastes were disposed of in the sinks. Additional information about the chemicals is available in the Supplemental Material.W

Figure 2. Students complete the worksheet using drops of reagents.

Results Students had to answer question A1 (Figure 1) that was about the relationship between chemistry and art and more specifically with painting. Before the project, 76% of the students could express the relationship of chemistry and art and give examples. After the lecture and the laboratory activities, 97% of the students could answer the same question. The students could express the relation between chemistry and art and give examples. After question A1 students had to answer question A2 that was about the contribution of chemistry to art, and name certain materials of chemical industry used in art. Before the actual teaching and the laboratory activities 54% of the students could express the contribution of chemistry to the arts and name materials of the chemical industry used in painting or in art. After the lecture and the laboratory activities 72% of the students could answer the same question and express the contribution of chemistry to art and name relevant materials. Data were tested with z statistical criterion that led to the conclusion that the difference of percentages is statistically significant: A1 versus B1, z = ᎑5.85, p < 0.001 and A2 versus B2, z = ᎑3.98, p < 0.001. Students were also asked about their feelings during the laboratory activity. The total number of the feelings listed was 144, 88.9% were positive (like exceptional interest, interest, joy, pleasure, enthusiasm, curiosity, surprise) and 11.1% of the total recorded feelings were negative (like stress, boredom, fear). Students completed their worksheet (Table 1) with certain chemicals that give characteristically colored products. Then, many students used paint brushes and the colored products on their worksheets as palettes to make simple watercolor paintings (Figures 2 and 3). The most common subjects were flowers, ships, and suns and they wrote captions or small phrases about their hometown, their football team, their boyfriend or girlfriend: I love (Mary, George, Tania, etc). Two remarkable phrases were “Chemistry forever” and “I love Chemistry”. The simple paintings, the positive feelings, and the questionnaires show that students enjoyed the process. We could say that art works of students constitute an authentic form of art and creation. They realized that reactants could be converted to colorful products. Students participated in groups transforming the school chemicals to personal art works. www.JCE.DivCHED.org

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Figure 3. Students’ colored worksheets and watercolor paintings.

Conclusion Students became familiar with some simple laboratory activities, such as the preparation of insoluble salts, and most students successfully completed their worksheets. Results of the questionnaires after the lecture and the laboratory activity show that the initial aim was successful and students realized the relationship between chemistry and art. The connection of (i) the properties of substances, (ii) the preparation of substances in the school chemistry laboratory, and (iii) the applications of substances in everyday life create excellent conditions of learning. It is statistically significant that pupils realized the contribution of chemistry to art and could mention chemical products, such as colors and solvents, that are essential for the purposes of art. This interdisciplinary and discovery learning method creates a fine learning environment, which leads to a positive attitude to chemistry and to the laboratory activities. Acknowledgment We wish to thank the reviewers for detailed and constructive comments. W

Supplemental Material

Information about the chemicals and a detailed student worksheet are available in this issue of JCE Online.


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Literature Cited 1. Pliny, The Elder. The Elder Pliny’s Chapters on the History of Art; Reprint Services Corp.: Temecula, CA, 1999; translated by K. Jex-Blake, commentary and historical inroduction by E. Sellers. 2. Cennini, Cennino. The Craftsman’s Handbook: “Il Libro dell’ Arte”; Dover Publications: Mineola, NY, 1954; translated by Daniel V. Thompson. 3. Dionysiou. Explanation of Painting, Mount Athos 1458, 1st ed.; Kalamata, 1981; Greek-language edition. 4. Harley, R. D. Artists’ Pigments, c. 1600–1835: A Study in English Documentary Sources, 2nd ed.; Butterworth–Heinemann: Oxford, 1982. 5. Hayes, C. The Complete Guide to Painting and Drawing; Phaidon: Oxford, 1979. 6. Kafetzopoulos, C. Chemistry for Conservators of Works of Art, 1st ed.; Papasotiriou Books: Athens, 1992; Greek-language edition. 7. Dawson, C. Int. J. Sci. Educ. 2000, 22, 557–570. 8. McGuffie, G. F. J. Chem. Educ. 1981, 58, 314. 9. The Chemistry of Art—A Sequel; Secondary School Chemistry (a series of articles) J. Chem. Educ. 1981, 58, 291–366. 10. Friedstein, H. G. J. Chem. Educ. 1981, 58, 291–295. 11. Werner, A. J. Chem. Educ. 1981, 58, 321–324. 12. Lambert, J. B. J. Chem. Educ. 1983, 60, 345–347. 13. Young, J. A. J. Chem. Educ. 1981, 58, 329–330. 14. NCW 2001: Celebrating Chemistry and Art (a series of articles). J. Chem. Educ. 2001, 78, 1295–1324.

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33. 34. 35.

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The Chemistry of Art and the Art of Chemistry - Journal of Chemical

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