Page:The History of Ink.djvu/25

Rh suspended in it, by gum, sugar or some similar substance which gives the quality of viscidity to its solutions.

The following will serve as a good formula for making common ink, and will be enough to give an idea of the ordinary and general mode of its composition:—"Take of Aleppo galls finely bruised, six ounces,—sulphate of iron, four ounces,—gum Arabic, four ounces,—water, six pints. Boil the galls in the water for about two hours, occasionally adding water to supply the loss from evaporation; then add the other ingredients; and keep the whole for two months in a wooden or glass vessel, which is to be shaken at intervals. Then strain the ink into glass bottles, adding a few drops of creosote to prevent mouldiness."

Besides its property of viscidity, the gum possesses the power of preventing the ink from being too fluid: and it also serves to protect the vegetable matter from decomposition. The great desideratum or requisite is that the ink should flow with perfect freedom from the pen, to allow rapid writing, and that it should adhere to the paper, or "bite into it," so as not to be effaceable by washing or sponging. The great defect to be avoided and prevented is the want of durability. The writing ink