Colored pencils containing oil or wax and similar pencils are not erasable. They consist in principle of pigments mixed with oil and wax and a solvent which evaporates once it is exposed to the air in a thin layer. There are also non-greasy colored pencils which can be brushed with water after drawing. None of these is very pleasant in consistency or effect. They may have some justification for taking notes in sketching, but have nowhere near the beauty of the erasable colors.
Copying pencils are totally useless. Their coloring matter is aniline dye and ink which combines chemically to some degree with the fiber of the paper when it is at all damp. There is always some dampness in all "dry" paper, so that, practically speaking, precipitation always occurs. Direct moistening with water makes the drawing run and blot.
Ball-point inks are made on the same principle; their rather viscous fluid is not composed of particles. The color is a soap-like solution colored with aniline dye. The solution dries out very quickly by evaporation, leaving an indelible mark. These inks are very sensitive to alcohol and ethereal oils like benzine and benzole, and they run and fade if they come into contact with them. This can happen even if there are gases from these oils in the air.
Apart from this disadvantage, the ball point pen can be an excellent instrument for small sketches and can make very delicate marks on paper, producing an effect like a pen drawing. It does not seem suitable for finished work, since the color appears not to be completely durable. If drawing inks, true inks, or liquid paints are used for drawing, pens or brushes are needed to transfer them to the ground. The classic liquid "color" for drawings is black drawing ink. We shall return in the section on Painting to deal thoroughly with the term "color," but we must here point out the many uses of the word. All attempts so far to find more precise terms and usages have failed.
Color means, first, that which is contrasted to black, white, and gray. Secondly, it can mean a pigment or coloring substance; this can include black, white, and gray. It also means pigment ready prepared for painting and drawing, either liquid in the form of a paint, or dry in the form of a pencil or chalk; and here, too, black, white, and gray are included. Thus, one can speak of black watercolor or white tempera color.
Watercolor is also a vague term. Literally it should include all paints which have water as a medium. This would include tempera, distemper, gouache, and ink. In fact, it is used only to describe colors which have a gum binder and are transparent.
Watercolor is, technically speaking, halfway between paint and ink. The latter, being a true solution of organic substances in water, is quite different chemically and physically. Ink makes a chemical precipitation on the fibers of the paper and is virtually irremovable; it can, however, be chemically changed, on the paper, into something colorless and hence invisible. Watercolor differs from ink in that the fine particles of pigment can be filtered out of the water, whereas in a true ink the coloring matter is in molecular form and passes through a filter as well as the water.
Drawing ink consists of very finely ground carbon suspended colloidally in pure water, with a binder. When brought into contact with paper or cloth, the carbon coagulates into larger particles and adheres to the surface indissolubly.
The binder used in ordinary commercially prepared liquid drawing ink, or India ink, is a mixture of shellac and borax, which cannot be dissolved in water once it has dried, but which will dissolve in caustic soda. The carbon used is not ground to the infinitesimal fineness at which colloids begin, even in the finest makes.
Carbon as used in genuine Chinese ink, which is a more complex mixture than the more popular India ink, is a very fine soot obtained by the incomplete burning of camphor oil. This soot is ground in water, a trace of glue, and various other materials of which the secret is not divulged, and pressed into a cake. The cake is pressed flat, ground down, and pressed again.
This tedious process, rather like making flaky pastry, is repeated several times until finally the cake, still in a malleable condition, is pressed into oiled moulds, which often have appropriate characters carved into them. Lastly, the moulded cakes are dried very slowly until they are as hard as stone and absolutely durable. They are often covered with real gold leaf and are much prized by collectors and command high prices, particularly those of great age - perhaps nearly a thousand years old.
In use, the cake is rubbed down with water in a fine porcelain dish, an extremely tedious operation. The ink thus obtained must be used immediately before it thickens in the water. It is a much more expressive medium than ink bought ready prepared in liquid form.
It is worthwhile rubbing down real Chinese ink if one's first preference lies in brush drawing, and there are now small electrical machines to grind it down. Chinese ink cannot be used with steel nibs, as it begins to harden on the nib, but a reed pen can be used. The water must be distilled.