Glazing as a practice in painting has been largely a technique of the past. Masters like Van Eyke, Vermeer, and Rembrandt used it as a matter of necessity, to hasten drying times of successive layers of oil paint. But the practice also endowed the artwork with a depth not found by mixing colors on the palette. Later, the impressionists, with the benefit of additional colors as well, preferred to use a wet into wet technique. Although, historically, the initial colored layer was anything from white, initially, to grey or brown by the seventeenth century, we will begin with a pure white background so as to maximize the brilliance reflecting back to the viewer.
Before progressing with the underpainting, a detailed drawing should be done. Many of the old Masters did a light drawing underneath their paintings, often in sliver-point, graphite, or chalk. Sometimes a light sketch with paints was done. Doing a drawing prevents corrections while painting. As glazing relies on the underlying colors in each part of the painting, corrections while painting will lead to more hassle than if the drawing had been corrected in the drawing stage. The drawing can be done either directly on the canvas or on a paper that is later transferred to the canvas.
After the drawing has been done, the underpainting, a blocked in version of the final painting, over the white ground can be done with a single transparent color, opaque colors, or a variety of different colors. A single color,such as grey or brown, gives the painting an internal harmony of hue, but I suggest that the underpainting be produced in a range of carefully selected hues. This is so the overlapping glazes have the most relevant hue beneath them. This calls for more forethought than underpainting in all one hue, but the results are worth it. The underpainting glazes should be created by mixing with water, for acrylics, or solvent, for oils. Watercolor, of course, uses water for all layers. Do not use glazing medium at this point so that there are no adherence issues to do with painting on top of a shiny surface. For acrylic and oil, the underpainting may also be done with opaque paint in places, but this is the only layer,other than final scumbling, where opaque paints should be used, because opaque paints, even when diluted, still tend to refract the light coming into the painting rather than letting the light shine through the layers and reflect back from the white ground. Note: as successive glazes are painted on the canvas, the amount of light reflected diminishes, so there is even a method of creating black from glazing.
After underpainting, the glazing begins. Glazing should be done in very thin layers. Each layer has to dry completely before the next layer is added on top. Keep in mind that the lines of the drawing have to keep sharp so that detail is not lost. For acrylics, acrylic matte medium and/or acrylic glazing medium should be used for mixing the glazes. For oils, different manufacturers have made particular flow mediums less viscous than linseed oil that are good for glazing. But keep the oil content to a minimum to prevent layers from ‘moving around’. Also, keep the layers as high in tone as possible as each layer is applied so that the layers do not become deep in tone too quickly and reduce the deepness and richness of the glazes. In order to successfully create the glazed layers, a good understanding of color theory is needed. Color theory will be the topic of a later post.
Subsequent to the glazed layers, scumbling may be used as a final layer. Scumbling uses opaque paints, often of a light tone. This paint does not completely cover the layers beneath. Use a drybrush technique to bring out high values. Rembrandt used scumbling to a high degree very successfully.