This exercise provides some insight into what the putty medium can do in terms of texture and in terms of creating translucent lighter values that are warmer than the same values made with white. Thus, there are many different temperature shifts within the grays possible in this exercise. They are slightly subdued in digital translation here but if you try this you'll see it clearly.

      Palette is set up as below, more on the putty medium itself here (text and formulas) and here (tutorial). The black and white are each cut with one part putty, then half is taken and cut again with one part putty until there are four dilutions. (This is of course arbitrary, could be more, especially with the white if you're using titanium,)

      Above is the image I'll be working from. There are elements of the composition I like but some elements that need to be changed, made more painterly. This exercise will allow the composition to be explored and simplified.

      The first pass is with the fifth black, very gray. No drawing, just looking for the major shapes and the composition, scrubbing the relatively tight paint with an older brush. In this image, I'll keep the paint tight for a while before blending it.

      The pass below is with the next darker black, quarter black. Still very casual, feeling the way while looking at the image.

      Now comes a pass with the one third black. A small amount of oil has been added to make some of the lighter values. Values can also be made with the end of the brush, the various squiggles.

      The next pass is with a clean brush and the most transparent white. This step can be a little jarring as the color of the white is noticeably blue in context. I'm putting this transparent white where the highlights are.

      The pass above is with the quarter white, then back to the brush with the half black, then back and forth with the two brushes. White is kept out of the darker values. A small amount of white may be in the middle values, or not. Stronger white can be in the higher values. The idea here is to stretch the value scale and give a sense of depth and dimension by the use of paint which is transparent, translucent, and opaque.

      This painting has more of an illusion of depth and color than might seem possible using black and white because there is in fact a difference in color between the grays made with the black used transparently, and the grays made with black and white. The grays made with black alone are warmer, and act as shadows. The grays made with a very small amount of transparent white act as midtones. The grays made with the stronger whites act as highlights. There was no pure white used in the painting.

      This is a simplified and abstracted example of one aspect of how older paintings were made which has become somewhat lost. The most important aspect of this system when working with color is not the local color - the "red" roof, the "green" grass - but working from the light-shadow axis of the day, setting up whether a given value is a shadow, a midtone, or a highlight. The corresponding paint then being transparent, translucent, or more opaque, which adds an element of color even while using black and white. This might be called painting from the envelope, because it begins by establishing the light-shadow envelope of the day. Once this envelope is established, local colors can be dropped into it without the laborious "hunt and peck" method of making each color correctly from scratch. This technique allowed older painters to maximize the sense of visual depth in the picture plane while using a palette composed of simple and reliable earth colors.