and soot,) is wholly unalterable in color by any of these chemical means.
Printing Ink (which is composed of carbon suspended in a drying oil) is, in essential characteristics, identical with the writing-inks of the ancient Romans and Greeks. It is impressed upon the surface of paper, (that which is unsized or bibulous being commonly preferred,) and is retained unchanged by the action of moisture, on account of the insolubility of the carbon and the repulsion between oil and water. These two forms of ink are therefore the exact opposites of each other, in the qualities on which their use and permanence depend. The most important peculiarity of the modern writing-ink, as contrasted with the ancient, naturally suggested the two names which it bore in the Latin and Greek of the middle ages, or (to speak more definitely,) the time of its invention and first employment. It was a Tincta, a DYE, or STAIN, which tinged and tinctured the material on which it was placed, entering among its fibres as coloring fluids do into cloth in the ordinary processes of manufacture. It penetrated the substance of the paper (as caustics or powerful chemical solvents and corrosives act on the organic fibre): it bit in, or burned in,—and was therefore well named ENCAUSTON and Incaustum.
