Glaze is a term for painting with a transparent medium. In other words, whatever is on the surface beneath the glaze will still be apparent after the glaze has been applied. The glaze will merely change the color cast of the surface. This is a technique that has been used for centuries in fine art. When using the techmique for wall glazing, the entire surface is generally covered often showing traces of texture(French Brush, Parchment, Striae, Rag Rolling). Either oil based or water based materials may be used for glazing walls, depending upon the desired effect. Kerosene or linseed oil may be used to extend the "open " or working time of oil based glazes. Water based glazes are sometimes thinned with glycerin or another wetting agent to extend the working time. In general, water galzes are best suited to rougher textures where overlaps of color are acceptable.