Eric Rhoades, age 13, of Willingboro, N.J., for his question:
HOW IS INK MADE?
Chinese and Egyptians had learned to make permanent black ink by 2000 B.C. They simply mixed lampblack or charcoal with glue or gums. Water was added when the ink was to be used. Even today, China or India inks, used for drawing and for permanent records, are made on the same principle.
Carbon in some form has been the basis of black inks for centuries.
Writing inks and printing inks are the two most widely used inks at the present time.
Most of the modern blue black writing inks are similar to the iron gall inks that were first used back about 200 B.C. They are made with tannic acid, gallic acid or both, as well as iron salt, a small amount of acid and water. A dye is usually added to give the bright blue color.
Early ink makers extracted their tannin from the galls they found on oak trees. For many years, each household made its own ink supply. Modern manufacturers buy their materials in a purified form.
Ink from ball point pens is transferred from the reservoir to the paper by a rotating ball that is locked in a socket at the writing tip of the pen.
The inks for ball point pens are different from ordinary inks. They contain more dye or pigment, they flow like heavy syrup and they do not contain water. They are usually made of dyes, slow drying solvents and resinous materials. About 25 percent of the ink is dye. The high dye content is needed because a ball point pen only deposits a thin film of ink.
Printing inks are made by grinding pigments into varnishes or other binders. The pigment is a finely divided solid that gives the ink its color. The varnish serves to distribute the ink on the press and bind the pigment to the paper.
The kind of ink needed depends on the type of paper or other material printed, the use of the printed object and the type of press used.
Viscous or syrupy inks used for lithographic and letterpress printing are made with varnishes that contain oils or similar materials. Linseed oil has been used for many years and is still used in making inks.
Other vegetable drying oils, oil like alkyd resins and other harder resins are now used in making inks of the same type. Mineral oils and rosin oil are used in cheaper grades of inks, such as news inks.
The inks are usually ground on a three roller mill. The pigment varnish mixture passes between the steel rollers, which press firmly against each other and rotate at different speeds.
Dryers are added during grinding or just before the ink is used. The common driers are compounds of cobalt, lead and manganese, which help to dry the ink quickly by absorbing oxygen from the air.
Silk screen inks are much thinner and flow more freely. The varnishes in these inks are made by dissolving resins in fast drying solvents