Media WC
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(Excerpts from ART HARDWARE: The Definitive Guide to Artists’ Materials, by Steven Saitzyk © 1987) Watercolor depends on the absorbency of the working surface and on the binder to remain where it is applied. If the surface is not absorbent, like glass or plastic, watercolor will crawl (an art term for the beading of water on nonabsorbent surfaces), rub, or flake off the surface. If very dilute watercolor is applied to a semi-absorbent surface, like a plate-surface bristol paper, there could be so little binder that the watercolor might dust off the way a pastel drawing might. If an absorbent paper, like a print paper, is used, the watercolor often spreads uncontrollably or sinks below the surface. The purpose of watercolor media is to regulate watercolors so that they can be controlled within a particular working situation, as well as to create special effects. GUM ARABICGum arabic is the binder for watercolor. It is also frequently used as a medium to help keep diluted watercolors from sinking below absorbent surfaces, to give a crisp appearance to the edges in a watercolor, to increase transparency, and to provide a varnish-like surface. Gum arabic is a natural gum, which is collected in the form of an exudate from branches of an African tree of the species acacia. The best gum arabic is collected from commercial plantations in the Sudan. The quality of gum arabic can be simply tested by dissolving some of the dry form in water, which should leave very little or no residue. The addition of a drop of iodine will indicate any added sugar (used as filler) by leaving a purplish color. A gum arabic medium can be prepared by adding one part dry gum arabic to two parts water and then slowly boiling until the gum is dissolved. A small amount of camphor (moth flakes) added to the medium will help to preserve it. Commercially prepared gum arabic media often have an emulsifier and glycerin added to improve handling. A thicker watercolor medium-a gel---can be made by the addition of silica. GUM WATERGum water is the name given to a diluted gum arabic medium that has a wetting agent. This medium allows for the addition of smaller amounts of gum for improving the transparency without decreasing the watercolor's ability to flow on the working surface. It is the wetting agent that prevents crawling, or beading, on less absorbent surfaces. AUXILIARY PRODUCTS FOR WATERCOLORThe following products are used to change, or control, the handling characteristics of watercolor. Ox Gall that has been clarified is a natural wetting agent for watercolors. It is used to reduce the surface tension between a watercolor and a less absorbent surface. However, only small amounts should be used and some caution is needed when using ox gall with colors that are made from pigments such as ultramarine blue, which are sensitive to acidity. Prepared Size is a product of Winsor & Newton Company. It is made from gelatin, water, and a preservative. The manufacturer describes it as "a soft gel which reduces the absorbency of paper, boards, and lightweight textiles. The gel becomes liquid on warming. Thinning is not normally required." This preparation achieves the opposite effect of that obtained with ox gall. Wetting Agents for Nonabsorbent Surfaces are commercially prepared and include Flex-opaque and No-Crawl, which are used primarily to allow the application of gouache on such nonabsorbent surfaces as clear polyesters and acetate. A small amount-a drop or two-added to a watercolor mixture will improve flexibility and help prevent flaking. However, if too much is added, the paint becomes tacky and will not dry properly. Masking Fluids, or Liquid Friskets, are like pigmented rubber cement. They can be painted on an area in which you wish to block the application of a watercolor. After the masking fluid is applied and has dried it will protect the surface, and when it is no longer needed it can be rubbed off easily. Luma Mask, Art Maskoid, Art Masking Fluid, and Miskit are some of the brand names for this pigmented rubber latex solution. These products should not be thinned or applied to a wet surface. (Excerpts from ART HARDWARE: The Definitive Guide to Artists’ Materials, by Steven Saitzyk © 1987)
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