ACRYLICS
The development of Western art over the centuries, the adoption of new artists' materials from time to time followed a definite pattern. No movements or schools of art began as a result of the discovery of new materials or inventions of new techniques. Rather, when new ideas and aesthetic departures arose, they created a demand for new technical methods that could express them in a more appropriate and fluent manner than was possible with the older methods. The pure egg tempera technique, for example, served painters from Giotto to Botticelli; it was ideally suited to the kind of pictures they wanted to paint. With the advent of new forms and new aesthetic and pictorial objectives, some painters began to modify their tempera by adding an oily ingredient, thus creating effects that cannot be duplicated by using straight egg tempera. At the same time or later, others overpainted their tempera paintings with oil and varnish glazes, especially at the fifteenth-century Flemish painters.
With the wider use of linseed oil, oil varnishes, and volatile solvents, and the further development in art forms that required a new kind of technique, straight oil painting was adopted. The entire development from tempera to oil paintings in Venice can be followed in the long life of one artist, Giovanni Bellini, who painted his earliest works tempera, after which he turned to intermediate tempera techniques, both oily ingredient and the glazed type, and finally to a technique aches the effects of straight oil painting. None of these new materials was invented for these purposes. They were already widely for their uses in other fields. Linseed oil, for example-its several of refinement and its use as a paint vehicle—was well known as a d and protective material at least as early as the fourteenth century.
POLYMER COLOR
The most widely used artists' colors based on synthetic resins are the polymer colors, made by dispersing pigment in an acrylic emulsion. These colors are thinned with water, but when they dry. particles coalesce to form a tough, flexible film that is impervious acrylic emulsion. These colors are thinned with water. But when they dry. The resin particles coalesce to form a tough. flexible film that is impervious to water The polymer colors have a number of excellent qualities for which they become popular. When they dry, they lose there solubility very rapidly, they may be made uniformly mat, semimat, or glossy by mixing them with the appropriate mediums. They are nontoxic, and become their thinning solvent with water. they are may be used aby parsons who are sensitive to allergic to the volatile solvents.
The name "polymer colors” has been adopted by general agreement. Although it is not specifically descriptive (since virtually every film-former is made of a polymer of some sort), it serves well to distinguish them from other paints made from synthetic resins, and it also replaces such loose terms as “the Acrylics" or "plastic paints.” Polymer colors are extremely versatile in imitating or approximating all the effects of the traditional water media. They are the first paints since oil colors that are sufficiently flexible to be used on canvas. With no other medium can a full-bodied, freely stroked or "juicy” effect be obtained with such dispatch. But polymer colors are not a complete substitute for oil paints, and artists whose styles require the special manipulative properties of oil colors, including finesse and delicacy in handling, smoothly blended or gradated tones, or control in the play of opacities and transparencies, find that these possibilities are the exclusive properties of oil colors. The polymer colors, however, are a boon to those painters to whom a high rate of production is important. A painting that might have taken days to accomplish in oil because of the necessity of waiting for layers of paint to dry can be completed in one session. The pigments are identical to those used in oil, except that the only white is titanium. An occasional pigment that works well in oil and watercolor (such as Prussian blue) is not compatible with the usually alkaline nature of the polymer medium, and so will not be found in the polymer palette. However, some of these pigments are currently being modified through resin encapsulation by manufacturers to prevent them from reacting with the alkaline acrylic polymer medium. More of the colors formerly omitted from the acrylic polymer palette will most likely become available in the near future. Acrylic paints are sold both in tubes and in jars. The colors in the jars are usually a bit more fluid than the tubed kind. Polymer paint films have extraordinary flexibility, an almost rubbery elasticity, which they retain without appreciable embrittlement for a long period of time during the same period of aging in which an oil-paint film would lose a measurable degree of its flexibility.
Painting with polymer colors over oil films is not recommended due to the very poor permanence of adhesion between the two pigmented layers. It has been recommended that an oil canvas or oil underpainting be roughened, to enhance the permanence of adhesion, by rubbing it carefully with extra fine sandpaper or steel wool before applying polymer colors, but the best procedure is to use polymer canvas or polymer primer (polymer gesso) and avoid combining the two in this manner. Although the straight polymer medium has the same excellent adhesive properties as the milky-white synthetic glues sold as general adhesives to oil-paint surfaces. Painting with oil colors over acrylic primer or acrylic under paintings is considered safe.
The actual amount of solid acrylic resin present in an acrylic is termed the “solids” the rest of the content consists of water, a film- forming and small quantities of various additives to precent potential problems listed above.