[Chris Saper]

HI Janel,

I am not sure your question relates to the layering of the painting from light to dark, its sequencing or both.

With regard to the layering, I think the medium drives most of those decisions. Watercolor, as described, needs to be layered from light to dark. For most painters that will also dictate the sequence with which one lays in color, but not necessarily so.

When working with pastels, it just takes much less effort to drag a light color over a dark than vice versa. In some cases, for example if the tooth is filled with light color, it can be virtually impossible to completely override the lights with subsequent layers of darks.

With oil I think that the layering of darks and lights depnds on several things. First whether you are an alla prima painter, in which case it is much harder to cover light areas with darks ( if not impossible) . Sometimes the layers simply need to dry completely, one at a time. The second factor I think has to do with whether you use Titanium (opaque) or for example Flake(transparent) whites in mixing your light tones.

The sequencing of light and darks is a different question: more than one school of thought, and all equally passionate. I have seen many oil painters begin with the middle tones, whether in toning the canvas or directly painting. I have also seen painters who immediately declare value "bookends" and work toward the middle values from each direction. They can both result in beautiful paintings.

In pastel work, painters commonly use a prepared ground in a middle value, in order to judge the relative lightness and darkness of colors they put on the surface. They might buy prepared colored surfaces, or create their own.

Watercolorists have no choice but to work on white, unless they will be mixing media, such as is frequently seen in watercolor/guache, where an opaque paint is used to restate light areas over already-colored parts of the picture.