This section is from the "Henley's Twentieth Century Formulas Recipes Processes" encyclopedia, by Norman W. Henley and others.
Heat 4 parts of water and 1 part of white wax over a fire until the wax has completely dissolved. Stir in 1 part of purified potash. When an intimate combination has taken place, allow to cool and add a proportionate quantity of gum arabic. With this mixture the desired colors are ground thick enough so that they can be conveniently rolled into a pencil with chalk. The desired shades must be composed on the grinding slab as they are wanted, and roust not be simply left in their natural tone. Use, for instance, umber, Vandyke brown, and white lead for oak; umber alone would be too dark for walnut use. All the earth colors can be conveniently worked up. It is best to prepare 2 or 3 crayons of each set, mixing the first a little lighter by the addition of white lead and leaving the others a little darker. The pencils should be kept in a dry place and are more suitable for graining and marbling than brushes, since they can be used with either oil or water.
See Etching, and Glass.