(7) A great deal depends on the proper quantity of water. A good ink must be completely dissolved, with no solid particles left. It should be about as fluid as a good, fat milk or vegetable oil. If it is too thick, it makes the work difficult. If it is too thin, it will not withstand the etching fluid. A few experiments will teach the proper proportions. Even a good ink will make poor lines if it is laid on too thinly and not firmly enough. This, however, is due to the artist's lack of skill or to defective pens, of which I will treat hereafter.
With this quantity of ink it is possible to work for a whole day. Thus each day fresh ink can be mixed; and it is to be noted that the vessels must be cleansed scrupulously that no trace of the previous day's ink be left in them. The ink will dry during the work, and as soon as this begins to interfere with its use, one or two drops of water will thin it again sufficiently.
This is about all that need be said about the chemical fatty or alkaline stone-ink in general. Particular remarks will be found in the description of its use for particular methods.
Besides the inks described, it is well to make the following and keep it in stock for uses whose great value will be explained later.
Shellac 4 parts Borax 1 part Water 16 parts
Borax and shellac must be put into a clean pot filled two thirds with water and boiled for an hour. As the water boils away it must be replaced. When the shellac has been mostly dissolved, the mass is removed from the fire, cooled, and filtered through a clean cloth to separate the undissolved portions of the shellac.
This solution can be kept for years in a tightly closed glass. To color it, a portion is to be cooked in a copper or iron ladle till it is thick as honey. Fine lampblack or vermilion is stirred in till the mass is thoroughly united. Then water is added, and the composition boiled again till it is a perfect solution. This black or red ink is first-class and can be kept well in tightly closed glass.
Herr Andre, in Offenbach, uses an ink which has the useful property of remaining good for years in fluid form. I do not find it so good for the very finest work as those I have described, but for music and script it is excellent. It consists of:--