Instructor Information
JCE Classroom Activity: #38
Pigments of Your Imagination: Making Artist’s Paints Nancy S. Gettys
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Journal of Chemical Education, Madison, WI 53715
Chemistry and Art is the theme of National Chemistry Week 2001, and this Activity was developed to help celebrate it. Painting is a popular form of art work. In this activity, students make and examine the characteristics of egg tempera paint. Available on JCE OnlineW are additional tips on making paint, instructions for making oil, water color, and acrylic paints, suggestions for further ac- Black egg tempera paint made with charcoal is tivities, and lots of color graphics. Our paint “recipes” are simpli- painted onto a wooden panel coated with gesso. A fied versions of those found in numerous references. An excellent close-up view of the paint is shown on the right. reference for anyone interested in paint and other art materials (1) was used as a general reference in the development of this Activity. Many excellent references are available online (2); also see student side and online supplement. This Journal issue contains numerous related articles (3).
Integrating the Activity into Your Curriculum In addition to making and testing paint, it is possible to emphasize the chemistry of paint and pigments, to study the history of the development of different types of paints, to attempt to duplicate commercial paints as closely as possible (see online supplementW), or to make paint using only everyday household items. The choice is left to the interests of the instructor and students. This Activity might be used to integrate chemistry into an art class. An art instructor or artist might speak to the chemistry class or try using the homemade paints.
About the Activity W
A steel wool pad (top) was rusted (middle) and ground into powder (bottom).
perforated
This Activity will require at least two days to complete. Using the online supplement, it could easily occupy students for all of National Chemistry Week. Part I can be completed in less than a full class period, but surfaces painted with gesso or house paint must dry overnight. Using commercially prepared stretched canvas or canvas board avoids this step. Several colors of egg tempera paint can be made and tested in a single class period. If you wish to have students paint a picture, they may need to pool their paint samples and additional time will be required. Pigment paste can be stored in a sealed container for several days, but egg tempera paint cannot be stored because it dries very quickly. It may be possible to borrow many of the materials for this Activity from your school’s art department. The least expensive paint brushes and supplies are suitable for this Activity. Many artists pigments are toxic and expensive. We list a few that are cheap, readily available, and safe for student use. A more extensive list of standard pigments and household items that can be used as pigments is available online. Suggested Pigments
Preparation (if required) and Notes
carbon, charcoal iron(III) oxide
Break up large lumps with a hammer before grinding. Produces black paint. Place a steel wool pad in a disposable cup. Saturate the pad with vinegar and leave exposed to the air. Stir or turn daily (2–3 days) until only rust is visible. Produces reddish-brown paint. Found in some “natural” sunscreens. Remove any oil that separates from the mixture. Produces white paint.
titanium dioxide, zinc oxide laundry bluing
Bluing is Prussian blue in aqueous suspension. Produces deep blue paint.
Answers to Questions
This Classroom Activity may be reproduced for use in the subscriber’s classroom.
fold here and tear out
Background
1. The most obvious difficulty is grinding solid pigments sufficiently to avoid lumps in the paint. 2. Egg tempera paints have vivid, transparent colors that dry very quickly with a glossy finish. Lumps of solid pigment (if any) may be easily scraped off. Otherwise, it should be difficult or impossible to remove the dried paint. 3. The chemistry of eggs is complex. Egg yolk is an emulsion containing oils along with proteins. When exposed to light and air, the proteins denature and the fats polymerize to quickly form a very strong adhesive. The proteins form hydrogen bonds with each other and with the surface, locking the pigments into a solid matrix. With time, covalent bonds are formed (1, 2). 4. Gesso seals and protects the surface so that paint does not soak through. The white background makes transparent colors more visible.
Literature Cited 1. Mayer, R. The Artist’s Handbook of Materials and Techniques, 5th ed.; Viking: New York, 1991. 2. Paints. http://cator.hsc.edu/~mollusk/ChemArt/paint/paints.html (accessed Aug 2001). 3. Denio, A. A. J. Chem. Educ. 2001, 78, 1298; Orna, M. V. J. Chem. Educ. 2001, 78, 1305; Frankel, F. J. Chem. Educ. 2001, 78, 1312; Jacobsen, E. K. J. Chem. Educ. 2001, 78, 1316; Judd, C. S. J. Chem. Educ. 2001, 78, 1322; Young, J. A. J. Chem. Educ. 2001, 78, 1326. JCE Classroom Activities are edited by Nancy S. Gettys and Erica K. Jacobsen
JChemEd.chem.wisc.edu • Vol. 78 No. 10 October 2001 • Journal of Chemical Education
1320A
JCE Classroom Activity: #38
Student Activity
Pigments of Your Imagination: Making Artist’s Paints
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Before there were art supply stores, artists had to make their own paints using whatever material was available. You can too! Paint contains two main components, a pigment (colored material) suspended in a medium or binder (substance that will permanently bind pigment to a surface). Egg yolk (an emulsion of fats and protein) is one of the oldest binders used by artists, and some artists still use it today. You can make egg tempera paint with ingredients found around the house or from a grocery store. (Ask your instructor about making other paints too!)
Try This You will need: newspaper, paper, cotton or linen cloth stretched over a frame, wood panel, white gesso or latex house paint, pencil, pigment(s), mortar and pestle, water, dropper, palette, eggs, toothpick, small containers for egg yolk and pigment(s), paper towels, rubber policeman or scraper, paint brush, and a palette knife or putty knife. I. Preparation
__1. Cover your working area with a layer of newspaper. Prepare several different surfaces on which to apply paint. Paper of various types, cloth stretched over a frame, and wood are good examples. Paint about half of each surface with gesso or house paint, and allow the painted surface to dry overnight. Use a pencil to mark areas (a few cm2 each) on each surface in which to test your paints. Draw a mark or design in each test area. __2. Your instructor will assign one or more pigments and will inform you of safety issues for each pigment. You will need about a teaspoon of each pigment. Grind dry, solid pigments into a fine powder with a clean mortar and pestle. Save the ground pigment in a sealed container. II. Making Egg Tempera Paint (repeat these steps for each pigment)
__1. Transfer about one teaspoon of powdered dry pigment to a clean mortar. Add a few drops of water and begin to mix and grind the pigment into the water. Continue adding a few drops of water while grinding until a thick paste forms. Grind until the paste is smooth, not lumpy or grainy. (You cannot over-grind the mixture!) __2. Separate an egg yolk from the white. Roll the yolk around on a paper towel to remove all white from its surface. Then, use a toothpick to poke a hole in the yolk sac and drain the sac’s contents into a small container. Discard the egg shell, egg white, and yolk sac, then wash your hands with hot water and soap. __3. Scrape the paste from step 1 (or place about 1/2 teaspoon of a cream-containing pigment, or several drops of pigment in aqueous suspension) onto a palette. Dip a clean paint brush into the egg yolk and use it to transfer to the palette an amount of yolk about equal to the amount of pigment. Mix pigment and yolk with a paint brush or palette knife. If the mixture is hard to spread, mix in a few drops of water. You have made egg tempera paint! III. Testing Your Paint (record all observations)
__1. Use a paint brush to apply paint to each of the surfaces you prepared in Part I. Can you paint one layer over another or see brush strokes in the paint? Add a few drops of water to some of the paint, then apply the thinned paint to the test surfaces. If several colors of paint are available, mix together a small amount of two colors. Do the colors mix well? Apply mixed paint to test surfaces. __2. Observe the painted samples at 10-minute intervals to determine about how long it takes the paint to dry. __3. When the painted samples have dried completely (may take overnight), use a palette knife or putty knife to scrape one portion of each sample and use a wet paper towel to scrub another portion.
Questions __1. Did you have any problems making your own paint? What were they? __2. Describe the characteristics of the paint you made—its brightness, transparency, color retention on drying, and time required to dry. Were you able to remove dried paint by scraping or scrubbing? __3. What chemical process occurs when egg tempera paint dries? Why does egg tempera paint have to be made with a fresh egg just before being used? Be Safe! Don’t in__4. Why apply gesso to cloth or wood before painting on it?
Information from the World Wide Web (accessed July 2001) 1. A Short History of Egg Tempera; http://www.eggtempera.com/history.html 2. Egg Tempera—Paintings by Rob Milliken; http://www.btinternet.com/~eggtempera/ 3. Paints; http://cator.hsc.edu/~mollusk/ChemArt/paint/paints.html 4. IMA Science & Art–Paint 1; http://www.ima-art.org/education/schoolprograms/science/paint.html
hale dust or powder. Never taste or eat anything in the laboratory. Wash thoroughly after handling raw eggs.
This Classroom Activity may be reproduced for use in the subscriber’s classroom.
1320B
Journal of Chemical Education • Vol. 78 No. 10 October 2001 • JChemEd.chem.wisc.edu
