 
|
 The medium of the paint layer is sometimes sufficiently hard and tough adequately to resist the effects of moisture, deleterious gases in the atmosphere, or of rubbing, vibration, and even blows. More usually, a protective layer has to be used. Ideally, this should be completely transparent, contain no substance likely to damage the paint layer, and be easily removable so that if damaged it can be taken off and replaced.Sometimes the protective coating serves as more than a protection and penetrates into the paint layer so that it serves in part as a medium. An example is in oil painting, where only a little medium has been used and much diluent. When the medium has hardened, the pigment may be incompletely enclosed, and the paint surface be dull; a coat of varnish will partly penetrate the paint layer, and help to bind it more firmly together, and also make it more transparent and darker in color. It is because of this penetration of the paint layer that in the case of certain processes, such as pastel and watercolor, a protective coating cannot be applied, without affecting the reflecting power of the pigment particles by making them more translucent and so darkening the color.
The protective coating, like other layers, does not necessarily consist of one material only. A layer of one may be superimposed on another, as when a coating of wax is applied to the surface varnish of a painting. The structure described above of five layers, each one again perhaps composed of further layers, is that of the most elaborate type of painting. The only layers that are indispensable, however, are the support and the paint layer. Some paintings consist of these only, others of three or four, instead of the full five layers. This fact provides a very convenient basis for classifying and describing various processes of painting. Those concerned with the simplest types naturally involve the least number of operations; and consideration of these leads on to that of the more complicated types and of how they are constructed.
Of the painting processes which require only support and paint layer, the most important and widely used are wax painting, pastel, and water-color. Two points should be noted: (I) that sometimes other layers may be introduced, such as a ground or a protective coating; (2) that the support sometimes has to be treated to modify its texture, and to make it more suitable to receive the paint layer. Though in fact this introduces a layer between support and paint layer, it is not strictly the introduction of a ground, but rather should be regarded as a modification of the support.
|
RSS Feed XML Sitemap HTML Sitemap Contact Us Privacy Policy