Pastels - Manufacturing the Chalks

Materials
Pigments - Poisonous pigments [lead whites, Naples yellow, chrome yellows and greens, cobalt violet, emerald green, cadmium and manganese colors) should be excluded from the pastel list as much as possible, and if any of them must be used, they should be handled with care. With these reservations, the pigments that are permanent in oils and water techniques are used, with the addition of whiting, precipitated chalk, and China clay.

Binder - See Table of Chalks and Binders
Gum Tragacanth
Alcohol
Water

Preservative
Beta naphthol or Dowicide A (sodium orthophenyl phenate).

Making the Chalks l. To make a batch of white chalks, use whiting (Paris white) pigment mixed with an equal volume of precipitated chalk, the total to weigh about 9 ounces. Add about 2 and 1/2 fluid ounces of Binder B. Mix these ingredients well, whether by using the mortar and pestle or the spatula and grinding slab. The consistency should be that of a stiff, slightly sticky dough or clay.

2. Take a small amount of this dough, and roll it into a rough cylinder. Place this on wrapping paper and roll it back and forth lightly with the flat wooden block to make the cylinder smooth. Be sure that the ends of the cylinder do not become hollow or deeply concave.

3. Set the finished crayon on a porcelain tray or a glass slab to dry at room temperature for a day or two. If a hard crust forms on the outside of the chalk when it is dry, scrape it off to expose the drawing surface.

4. Before making up the whole batch of crayons, make a sample and dry it thoroughly over a radiator or stove. Test it when it is dry to see that it is not too hard or too soft. The pigments may need an adjustment of the amount of binder used, some needing the strong Binder A and others the dilute B or C. Still other pigments will need only water since they seem to have some naturally cementitious quality. Pigments of the same name sold by different firms may vary considerably, and so the following table, indicating the pigments and their binders, should be used only as a stating point.

5. Mixtures of colors can be made by mixing the dry pigments before adding binder. However, to insure the proper mixture of binders in proportion to the mixture of pigments, it is easier to mix each of the pigments with the binder that is proper to it. Then the pigment-binder pastes can be combined. For example, to make a set of raw sienna chalks, mixed with white to produce graded shades, the following procedure is used:

a). Prepare a good-sized batch of white pigment with Binder B as in step l.

b). No. 1 Full Strength Raw Sienna. Make a batch of pure raw sienna combining raw sienna pigment and Binder E. Form one half of the batch into chalks, which will be labeled no. 1 Full Strength Raw Sienna.

c). No. 2 half Strength Raw Sienna. Mix the other half of the pure raw sienna paste with an equal volume of the white pigment paste. Combine them thoroughly so there are no streaks in the mixture. Form half of the mixed paste into chalks, which will be labeled no. 2 half Strength Raw Sienna.

d). No. 3 One-Quarter Strength Raw Sienna. Mix the other half of the no. 2 mixture with an equal volume of white pigment paste. Form half of this paste into chalks, which will be labeled no. 3 One-Quarter Strength Raw Sienna. Set the other half aside to be mixed with an equal volume of white pigment paste to make a still lighter chalk. Repeat the process as long as lighter shades are desired. The same method may be used in making any color combinations.

[pp. 206-209]