( Originally Published 1937 )
APART from the essentially decorative qualities of the forms of the pottery itself and the colors of the glazes, decoration of pottery may be classified roughly into two kinds.
Three-dimensional is the enrichment by actual manipulation of the surface.
Coil pots easily lend themselves to a decoration of this kind. By rolling the coils carefully and pinching them together at `regular intervals patterns can be made of the contrasting texture of the pinched and unpinched parts of the clay.
Lines may be made on a thrown pot while it is revolving, by holding a stick against it.
Decorative forms can be modeled on a damp pot with soft clay, or built up with slip.
Designs may be incised with a modeling tool, cutting out the background and leaving the pattern raised. The reverse is also good.
Two-dimensional is surface enrichment in mono-chrome or color.
Colored slips may be applied in plain bands or shaded from dark to light, by brushing them onto a pot while it is revolving on the wheel. Underglaze colors mixed with a little clay may be applied to dry or biscuit pots the same way, or used to do freehand brush decoration. This is great fun, and produces charming results. Enough clay should be mixed with the color to insure its holding well under the solvent action of the clear glaze which is to cover it.
Oxides or underglaze colors mixed with clay are pressed into incised decorations and scraped or burnished smooth. This burnished pottery is beautiful if waxed instead of glazed.
Overglaze colors are mixed with a little molasses or gum arabic and painted on top of the glaze, then fired at about cone 015 or lower. This is a very easy way of decorating pottery, but it does not give the depth and character of underglaze work.
Model with soft clay or build up with slip of a color different from the background. The French pate-sur-pate and the English Wedgewood are well-known examples of these methods, applied to porcelain.
Sgraffito is an Italian version. Dip the damp pot in a slip of a different color. When it is leather hard, cut through the coating of slip, and peel it off in patterns, exposing the body color for a background.
For stimulating suggestions for decorative motifs, I recommend Adolfo Best-Maugard's book: A Method for Creative Design.