Ratio of encaustic to pigment stick is very important. The rule of thumb when adding anything to encaustic is to keep the ratios consistent (see How to Make Encaustic Medium and Paint), if incorrect, all the binding properties fail, resulting in a painting that will crack, chip, slag and more. Paint Sticks consist of, amongst other things, linseed oil. Using a small percentage of oil in encaustic has been a long tradition; therefore, adding a oil based product such as pigment sticks should not be a problem. It can help with the toxicity level to eliminate linseed oil from your encaustic paint or medium (obviously this requires making your own paint), but it is not necessary.Problems occur when to much paint stick is used: when using a paint stick traditionally, as a drawing medium, remember that the ratio of paint stick to encaustic is, to the amount which is on the surface of your support, not how much is on your palette, or in the block of encaustic, or in your palette cup. You are typically adding the paint stick to the surface, not in the encaustic mix itself; the surface is only a fraction of an inch thick, so it is easy to over-do.
How much is the correct amount? Paint sticks should only be used in minute/thin amounts. The easiest way to learn is to make some samples and test different thicknesses of paint stick on the encaustic and fuse as you regularly would. If you are applying at the end of a finished encaustic piece, and do not plan to paint more wax on, you can be less critical about your ratio of wax to paint stick.
Also read, Oil Paint as Pigment
and more on Oil Pastels- coming soon.
