The lampblack must be of the finest sort, and should be roasted and burned in a closed vessel until it ceases to give off any yellow smoke.
When everything has been stirred till the mass is nearly cold, it is kneaded into any desired shape, sticks being the best, and so saved for use.
The following remarks are to be noted especially:—
(1) The soap is to be the ordinary soap made from ox fat and lye. In the formulas its weight is calculated in fresh form, which, of course, includes considerable water. If the soap is very dry, less must be used.
Venetian or vegetable oil soap is not so good because the ink easily becomes slimy afterward when dissolved in water. It does not resist acids so well, either. If, however, the other kind is not to be had, or to be had only in poor quality, the Venetian soap will do. It will be necessary merely to make frequent fresh solutions in water of the ink.
(2) Lampblack is not the only substance available for giving color to the ink. Vermilion, red chalk, indigo, blue lake of logwood, and several other colors can be used, so long as they do not consist of acids or other salts, and thus have properties that could alter the nature of the soap. The finer kinds of ordinary lampblack can be used without burning, but then a part of the soap always is rendered inactive, because the lampblack usually contains a considerable quantity of inflammable wood acid which unites with the alkali, neutralizes it, and thus destroys its effectiveness against fats. Therefore, if it is not roasted beforehand, it may be necessary to mix more soap with the ink after it is made, and this does not completely remedy the trouble. Lampblack can be purified by rubbing down with strong lye and then boiling in sufficient water till no trace of alkali remains, if roasting and burning be undesirable for any reason.
Better even than this purified lampblack is one that one makes for himself from ox or other animal fat, from wax, or better still, from a mixture of ox fat and resin. The fat is melted and poured into an earthen lamp similar to those used for city lighting, with a cotton wick. The lamp is lit and placed under a plate of iron or brass, so that the smoke must settle on it. The plate must be close to the flame. The soot is scraped off from time to time and dropped into a glass, which is kept covered. This process continues, the lamp being refilled till one has the desired quantity. This soot is very fine and bland, and so good that one can do more with an ounce of it than with three ounces of the ordinary kind. The ink made from it is extraordinarily fine and good.
It is to be noted in conclusion that the more soot is used, the blacker will be the ink, but the coarser will be the work, because the ink will have the tendency to spread. The less soot is used, the finer will be the work; but it is not easy then to see what one is doing or to judge if the design is strong enough. The quantities given in the formulas appear to me to be the best, especially if the self-manufactured soot is used.
(3) To dissolve the ink, rain water or pure soft river water is best. The rain water must not be very old or stale, otherwise the solution will get slimy.
(4) The severe combustion is not vital for making the ink, but helps very much in making it easy to use.