A few days ago, I was really sick of the flood of assignments that I had to deal with, so I decided to devote some time to my hobby for a change. Drawing is one of the best things I like to do most, and for coloring I use colored pencils habitually because of its convenience. However, on that day, I was already tired of holding a pencil and felt like holding a paintbrush instead. So I pulled my watercolor set that was not used for a long time from my room. Then I thought, “Although I own many painting tools, and have noticed of words like pigments, I’ve never wondered how these actually work. If I could figure out what is happening inside these paints, that knowledge will not only be useful when I paint, but it should also form a bridge between the world of science and art in my mind.” So I decided to use this opportunity to do a research on how chemistry is involved in the manufacturing process of paints.
Each paint manufacturer has their original composition – a basic recipe for their products – that is designed to keep the costs under control and to get the best possible handling attributes for every pigment in the watercolor line. However they often use the same ingredients. (Figure1)
(1) One or more pigments, which will add color to the paint. (2) A brightener, white or transparent crystals that will brighten the dried paint. (3) A binder, as known as gum Arabic or synthetic glycol that makes the paint to form a film when dried. (4) A plasticizer, often glycerin, to help the binder to redissolve. (5) A humectant, traditionally simple syrup or honey but now often inexpensive corn syrup, to help the paint retain moisture. (6) An extender or filler, such as dextrin, to thicken the paint without affecting the color. (7) Manufacturing additives, such as dispersant and preservatives. Dispersants prevent clumping of the raw pigment after manufacture and speed up the milling of ingredients. Fungicide is added as a preservative and suppresses the growth of mold or bacteria. (8) Finally, the water, which dissolves or suspends all the ingredients, carries them onto the paper, and evaporates when its work is done. (MacEvoy, 2005)
After looking at the function of each ingredient in watercolor paint, and found out that pigment is the one in paint that’s actually creating all kinds of vibrant colors, I got curious and did some further research on pigments. Pigments are very fine powders that have their own color, chemical, and physical properties. (Matsukawa, 2002) They are usually of mineral or organic origin although some, such as lead white, are artificially produced. (Janson, 2013) For example, Cobalt blue that artists use it for high quality blue, chemically is a Cobalt(II) aluminate, CoAl2O4, a product of reaction between Cobalt(II) chloride and Aluminum chloride. The two substances undergo a “sintering” process, that is, they are grinded together, then heated to form a bond. (Chemicalland21, 2013)
For this reason, chemical reactions play an important role in the manufacturing stage of paints to offer us a wide range of colors. However, once the paint comes into action, the chemical reaction can mess around with our artwork. I assume that most of the artists would have encountered this problem at least once: One puts his work on sunny place to let it dry, then he notices a slight color change when the artwork compared to when it was still wet. I read an interesting article about Van Gogh’s painting losing their shine due to chemical reaction, reciting that, “The yellow pigment, used by Van Gogh has been undergoing a chemical reaction when exposed to ultraviolet light (including sunlight) that turns the outer layers of the painting brown. …This sunlight triggers a chemical reaction that turns the bright yellow into a dirty brown. “(Welsh, J) This change of color was caused because the Chromium in the yellow pigment had gained electrons due to the UV light from the sun, hence reduced to Chromium(VI) to Chromium(III).
It is such a wonder that chemistry can both enhance and spoil the beauty of art. This research had raised my knowledge as an art student, and more importantly, it also made me want to dig more into the world of chemistry, in other words it strengthened my curiosity. In my opinion being curious about what kind of science is involved in the real world is necessary for IB chemistry students. In conclusion, this research had taught me that being vividly aware of science behind any subjects can benefit us in many aspects.
MacEvoy, B. (2005). how watercolor paints are made. handprint. Retrieved from http://www.handprint.com/HP/WCL/pigmt1.html.
Matsukawa, N. (2002). What is PIGMENT?. All about painting materials and Techniques. Retrieved from http://www.cad-red.com/mt/b_pig.html.
Janson, J. (2013). The Anatomy of Pigment and Binder. Vermeer’s palette. Retrieved from http://www.essentialvermeer.com/palette/palette_anatomy_of_paint.html.
AroKor Holdings Inc. (2013). COBALT BLUE. Chemicalland21. Retrieved from http://chemicalland21.com/specialtychem/NH/COBALT%20BLUE.htm.
Welsh, J. (February 14, 2011). Chemical Reaction Darkens Van Gogh Luster. LiveScience. Retrieved from http://www.livescience.com/12852-chemical-reaction-darkens-van-gogh-luster-110214-html.html.
MacEvoy, B. (2005). schematic backbone composition of a modern watercolor paint. handprint. Retrieved from http://www.handprint.com/HP/WCL/IMG/backbone.gif.
Hafizov, I. (n.d.). pigments. Chemistry Explained. Retrieved from http://www.chemistryexplained.com/photos/pigments-3462.jpg.