Appreciating the Colors

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.

(Figure 1)

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.

References

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.

Images Cited

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.

One thought on “Appreciating the Colors

  1. UV Rays: “the invisible murderer” and its effect on our lives

    I truly enjoyed reading Mika’s blog post about the chemistry of watercolor paints; her statement that “chemistry can both enhance and spoil the beauty of art” made me marvel once again, about the power of chemistry and the relevance of chemistry to our everyday lives. After learning that UV rays caused damage to the Van Gogh art piece, I decided to do more research on the effects of UV rays not only on art, but also directly on our lives, including our skin and drinking water.

    I do not consider myself to be an artist (I’m not very good at art ☺), but the beauty of many masterpieces by artists like Van Gogh has always fascinated me. When Mika mentioned “an interesting article about Van Gogh’s painting losing its shine due to chemical reactions”, I immediately clicked on the link and was intrigued. In the Van Gogh painting Mika talked about, UV light was the main culprit as to why the yellow pigment became brown: the UV light caused the chromium metal to gain electrons—one pigment constituent, chromium, was reduced from chromium (VI) to chromium (III). (Welsh, 2011)

    Image 1: The Predicted Change in Color of Van Gogh’s Painting

    From common knowledge, I’ve always known that pigments fade after a period of exposure in the sun. For example, the vibrant colors of signs always become lighter and more pastel looking after a long period of time. This is actually, according the Library of Congress Science Reference Services (2010), a process called photodegradation. Light is a form of energy, and consists of photons. When substances, such as pigments absorb it, the photons actually transfer electrons to the substance to reduce it and thus change its nature. As I learned from IB Chemistry, on the electromagnetic spectrum, UV rays have very high energy and is invisible to the human eye. In this case, the chromium is reduced after absorbing the high energy of UV rays, as seen in the chemical equation of Cr6+ → Cr3+ + 3e-.

    According to Florida Solar Energy Center (2007), the sun’s energy has three components: “ultraviolet radiation, visible radiation, and near-infrared radiation.” Ultraviolet rays are not the sole cause of color fading, but they are the main cause. Something worth noting is “Protecting against UV is not just important in hot, sunny climates. Even in cold, cloudy climates, UV radiation can damage furnishings.” (Florida Solar Energy Center, 2007)

    Last summer, when I visited Paris, I remember that almost every museum posted noticeable signs prohibiting visitors to take photos using flash. I did not question why, and just assumed that it was not to disturb other visitors, but now I understand—energetic photons are potentially damaging as they can change the chemical nature of the pigments. An important responsibility of museums is to preserve the art pieces, so banning flash photography would be important in making sure that the chemical makeup of the art pieces does not change.

    It’s so interesting to make connections using chemistry; as an IB Chemistry student, these discoveries are increasing my awareness, as well as curiosity, of the world around me.

    Reading about the damaging effects of UV light on pigments reminded me of my obsession with sunblock. As many members of the cross-country team know, I am probably the only person who insists on wearing sunblock every day before practice. I have always assumed that sunlight is bad for my skin because my mom told me that skin cancer was caused by too much unprotected exposure to the sun. Our skins cells certainly can’t be reduced like chromium metal, then how does UV light harm our skin?

    There are two types of UV rays that reach the earth, UVA (long wave) and UVB (short wave). (Skin Cancer Foundation, n.d.).

    Image 2: UVA and UVB Rays on our Skin

    When UVB rays reach our skin, they are relatively shorting, so they usually cause burning; when UVA rays reach our skin, however, their longer wave length allows them to penetrate into our DNA. (Skin Cancer Foundation, n.d.) Our DNA normally consists of two strands with nitrogenous bases bonded together by hydrogen bonding. Adenine bases bond with guanine, while thymine bases bond with cytosine. According to the educational webpages of Clinuvel (2010), however, UV light acts as a carcinogen because when our skin is exposed to it, the UV rays alter the chemical bonds in our DNA. The hydrogen bonds between matching bases break and the wrong bonds are formed: dimers form between adjacent nitrogenous bases on the same strand instead of opposite nitrogenous bases from two strands. For example, usually, there is a hydrogen bond between Guanine and Cytosine, two matching nitrogenous bases. After absorbing the UVA ray’s high energy, the bond breaks, and Cytosine makes a bond with Adenine, a nitrogenous base on the same strand that does not match. The image below illustrates this mutation.

    Image 3: DNA Dimers caused by UV Rays

    Normally, our body has systems to repair our DNA (Clinuvel, 2010); thus, we usually do not get skin cancer with moderate exposure to sunlight. It is important, however, that we do not stay in the sunlight for long periods of time, as permanent DNA damage that causes skin cancer may potentially occur. Also, we often think that our skin will not be exposed in rainy days. However, it is important not to be deceived, because UV lights are invisible to the human eye–we can potentially damage our skin as long as we are under open air.

    As I learned when revising my previous blog post, it is important to have different perspectives when we view things. UV light may have harmful effects on our skin or valuable paintings, but it has beneficial qualities as well.

    One example that we have discussed in IB Chemistry class before is the ability of UV rays to disinfect water—the property of UV rays to damage nucleic acids and other vital cell components allows UV rays to disinfect water through a photochemical reaction that damages the genetic material of microorganisms and bacteria. The chemical composition of the water is not affected by the UV rays, but the microorganism cell walls are absorb the high energy and the cells consequently die (National Environmental Services Center, 2000).

    I have always wondered how UV radiation could be safe–what if the water we drink has radioactive residue? Isn’t that extremely dangerous? The answer, however, is that the UV rays quickly dissipate in the water, and are just as quickly absorbed or reflected off, thus leaving no residue at all.
    Another excellent property of UV disinfection is that the various chemical properties of water contaminated to different degrees do not effect the potency of the UV rays. For example, different pH or temperature does not change the effectiveness of UV rays. One drawback, however, is that some suspended matter in the water, including irons and sulfites, absorb UV light and shield microorganisms from disinfection. (Environmental Protection Agency, 1999)

    Mika’s blog post on the chemistry of different colors was very informative; in the end, her mentioning of the damage Van Gogh’s painting underwent due to UV light inspired me to look into how UV light chemically damages and benefits our lives. It is important for us to limit our exposure to the sun, yet the same damaging effect of UV rays can be used to our advantage when we disinfect our water. It’s very interesting to see how everything from cancer to disinfection has to do with chemistry—science is truly applicable to almost every aspect of our lives. In addition, I learned to look at one thing from different perspectives by researching not only the damage UV rays cause, but also the benefits as well.

    References:
    Clinuvel Pharmaceuticals Ltd (2010, May 12). UV Damage and Carcinogenesis. Retrieved May 2 from http://www.clinuvel.com/en/skin-science/skin-sun/skin-cancer/uv-damage-and-carcinogenesis

    Columbia University (n.d.). DNA Dimers [Online image] Retrieved May 2 from http://eesc.columbia.edu/courses/v1003/images/UV.rad.dimers.jpg

    Environmental Protection Agency (1999). UV Chemistry (Photochemical). Ultraviolet Radiation. Retrieved May 28 from http://water.epa.gov/lawsregs/rulesregs/sdwa/mdbp/upload/2001_01_12_mdbp_alter_chapt_8.pdf

    Florida Solar Energy Center (2007). UV Transmittance and Fading. Retrieved May 2 from http://www.fsec.ucf.edu/en/consumer/buildings/basics/windows/fading.htm

    Library of Congress (2010, August 23). Why Does Ultraviolet Light Cause Color to Fade? Everyday Mysteries. Retrieved May 2 from http://www.loc.gov/rr/scitech/mysteries/colors.html

    National Environmental Services Center (2000, September). Ultraviolet Disinfection. Tech Brief. Retrived May 2 from http://www.nesc.wvu.edu/ndwc/pdf/ot/tb/ot_tb_f00.pdf

    Scientific American (n.d.). Van Gogh Estimated Color Change. [Online image] Retrived May 2 from http://blogs.scientificamerican.com/media/inline/blog/Image/van_gogh_yellow_paint.jpg

    Skin Cancer Foundation. (n.d.) UVA & UVB. Retrieved May 2 from http://www.skincancer.org/prevention/uva-and-uvb

    University of California San Francisco School of Medicine (n.d.). Skin Cancer [Online image] Retrieved May 2 from http://www.dermatology.ucsf.edu/skincancer/images/UV.gif

    Welsh, J. (2011, February 14). Chemical Reaction Darkens Van Gogh Luster. LiveScience. Retrieved May 2 from http://www.livescience.com/12852-chemical-reaction-darkens-van-gogh-luster-110214-html.html.

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