GEOLOGY 640: Geology through Global Arts and Artifacts LAB 9: MAKING PAINTS FROM NATURAL MATERIALS Paint is a mixture of microscopic grains of pigment that are suspended in a liquid vehicle. A pigment is an insoluble colorant, in contrast to a dye in which the colorant is dissolved. The vehicle in which the pigment is dispersed for watercolors is a mixture of materials with specific purposes: • Binder adheres the pigment to the page. Gum arabic is a commonly used watercolor binder. It is a natural, water-soluble gum that is produced by acacia trees of the middle east and northern Africa to seal wounds in the bark. Starches and animal glues also are used. • Plasticizer, such as glycerin, helps to soften the binder and help it to redissolve • Humectant , such as honey or corn syrup, helps the paint retain moisture Gum arabic on acacia tree Making Watercolor Paint (from www.handprint.com) Pigment Powder • Grind the sample of the mineral pigment (e.g., hematite, limonite, glauconite) using a mortar and pestle. • Pour the powder into a beaker of water and mix well • Wait 1 minute for the coarse grains to settle, then pour off the water and suspended pigment into another container • Allow 2 days for the pigment to settle, then pour off the water • Allow the sediment to dry, then powder and store it. Examples of Common Mineral Pigments Mineral Formula Mineral Class Color Common Name Hematite Fe 2O3 Oxide Red Red Ochre Magnetite Fe 3O4 Oxide Black Limonite FeO[OH]·nH 2O Hydroxy-oxide Yellow Yellow Ochre 3+ Glauconite [K,Na][Fe ,Al,Mg] 2[Si,Al] 4O10 [OH] 2 Clay Green Green Earth Kaolinite Al 2Si 2O5(OH) 4 Clay White 1 Examples of Exotic and/or Toxic Mineral Pigments Mineral Formula Mineral Class Color Common Name Cinnabar HgS Sulfide Red Vermilion Orpiment As2S3 Sulfide Orange Lazulite (Na,Ca) 8(AlSiO 4)6(SO 4,S,Cl) 2 Tektosilicate Blue Ultramarine Azurite Cu 3(CO 3)2(OH) 2 Carbonate Blue Malachite Cu 2(CO 3)(OH) 2 Carbonate Green Cerrusite PbCO 3 Carbonate White Lead White Rhodochrosite MnCO 3 Carbonate Pink Gum Arabic Solution • Place 1 part gum arabic powder or crystals in a saucepan. • Heat 2 parts distilled water to a boil, remove from heat, and slowly pour over gum arabic, stirring to mix. • Add one part glycerin per 5 parts gum arabic solution. • Add one part honey per 10 parts gum Arabic solution. • If you intend to keep the paint for a while, you can add a few drops of oil of clove as a preservative • Cover with cheesecloth and let stand for one day, stirring occasionally. (Some gum crystals may need longer to dissolve.) • Strain the solution through several layers of cheesecloth to remove impurities and sediment. Paint Mixing • On the glass sheet or stone countertop, make a pile of about 1-1/2T of pigment powder. For gouache (an opaque watercolor paint) add 1/4 T of calcite powder (whiting). • Use the back of the measuring spoon to make a hollow in the center of the pile. • Pour 1 t of gum Arabic solution into the hollow, and knead very slowly with the putty knife. As needed, add more gum arabic solution or distilled water until pigment forms a creamy paste. • Use a muller to break apart and grind the pigment aggregates. You cannot overwork the paint; usually 1 hour of steady mulling is minimally sufficient. Add more vehicle or water as needed to counteract evaporation. • Cover the mixture with cheese cloth and allow to stand, folding occasionally with the putty knife, until evaporation reduces it to the desired viscosity. 2 Work in groups of 4 or 5 to prepare a palette of colors of gouache paints using the preceding directions. Four common mineral pigment powders are provided (hematite, magnetite, limonite, glauconite). In addition you will need to prepare a powder of kaolinite. Because gum arabic requires at least 24 hours to dissolve, the gum arabic solution is provided. Divide the paints so that each group member has a complete palette. Take home your paints. Research a culture that uses/used a limited color palette such as the one that you created from common minerals (red, black, yellow, green, and white) (e.g., cave paintings, Australian aborigines, native Americans, African tribes). What materials did they use? From where did they get their materials? What role did their paintings play in their culture? Did certain colors/pigments have certain meanings? Write a one-page summary of your research. Create a painting in the style of your selected culture on an appropriate piece of earth material (stone, wood, tile, etc). Bring your art work and report to class next week, and be prepared to present your work to class. (The instructor will select a few students to describe their painting in context to the culture that they studied.) 3 .