The black is washed and dried, then mixed with linseed oil, and an ink is obtained suitable for printing, lithography, and wood or metal engraving, (e) The base of common printing ink is a linseed-oil varnish, which sometimes possesses a disagreeable odour, and the ink made from it smells so badly as to make a freshly-printed paper an unpleasant companion for sensitive nostrils. Dr. Bracken-busch, of Berlin, proposes to overcome this disadvantage by replacing the linseed varnish with a solution of colophony (rosin) in paraffin oil. He dissolves 45 parts of fine rosin in 25 parts of paraffin oil by heating them to 176° F. (80° C), or by mixing them with a machine at ordinary temperature. When the solution is effected, if such it may be called, 15 parts of soot or lampblack are added. (f) Persoz and Jeanolle make ink for letterpress-printing, lithography, and autography, from the refuse of the gasworks, from other tar, and the heavy oils of petroleum, resin, wood, etc. They say that these substances present valuable qualities for the purpose, that they mix readily with lampblack and other dry colours in powder, and that the ink made from them has the great advantage of neither penetrating the paper nor spreading; and lastly, that it may be mixed in any desired proportions with the fatty oils for certain classes.

For black imk for typographic printing, the inventors use what they call evaporated tar, or liquid pitch, with lampblack and Prussian blue, in the following proportions: - Tar, 100 parts; lampblack, 36; Prussian blue, 10; glycerine, 10. (g) Colo-phonic tar, 14 lb.; lampblack, 3 lb.; indigo, 8 oz.; Indian red, 4 oz.; yellow rosin soap, 1 lb. The colo-phonic tar referred to is the residuum from the distillation of rosin for rosin-, oil. (A) Linseed-oil, 40 gal.; litharge, 4 lb.; lead acetate, 2 lb. The oil is heated to about 600° F. (316° C.) for 48 to 65 hours, according to quality of varnish required, the lead salts being added as driers. To each gallon of this varnish, 4 lb. of gum copal is added and dissolved. For common news ink, the proportions are as follows: - Of the above varnish, 15 lb.; rosin, 10 lb.; brown rosin soap, 2 lb.; lampblack, 5 1/2 lb. (i) A fine ink, suitable for use with rubber type, is prepared from soluble nigrosine, 1 oz.; pure glycerine, 4 1/2 oz.; white curd soap, 1/4 oz.; water, q.s. The nigrosine, finely powdered, is mixed into a stiff paste with the water, hot, and after standing a few hours, this is mixed with the glycerine and soap, and the paste is rubbed down with a muller on a hot stone slab.

(B.) Coloured. - Printing-inks may be made in a number of colours besides black. The principal are the following: -

Blue

(a) Indigo gives a deep but dull blue; it is cold but permanent. (6) Prussian blue needs much grinding, and extra soap; it affords a deep bright colour, and is useful for making greens, (c) Antwerp blue is easily ground to the proper degree of fineness, makes a good ink, and .works clean and well; its tint is bright and light, with a slight green tendency.

Green

Various shades of green may be produced by suitable admixture of blues and yellows. Prussian blue and chromate of lead make a good rich green; indigo and the same yellow, a deeper, duller colour; Antwerp blue and the same yellow, a brilliant rich green. The chromate must be quite pure to ensure bright colours.

Purple

Different shades of purple may be made by grinding together carmine or purple lake, with Prussian blue.

Bed

(a) Carmine may be readily ground into a fine ink of brilliant colour by admixture with black ink varnish made with balsam of copaiba. It is expensive, but valuable for special purposes. (6) Crimson lake is easily reduced by the muller; it works clean, and does not require more soap than is contained in the varnish, but it does not possess much depth, (c) A deeper tone than can be obtained from commercial lake may be produced in the following manner: - 1 oz. best cochineal, powdered, and boiled in 1 qt. water, till the colouring matter is extracted, let the cochineal subside, and pour the liquid into another vessel; when cold, gradually add some chlorate of tin, with constant stirring, till the supernatant liquid, on standing, becomes nearly colourless; then add a little powdered alum. Assist the solution by stirring; allow to subside; pour off the excess liquid; wash the coloured residue with 3 or 4 waters, to remove the acid; and dry carefully and slowly. The addition of cream of tartar during the process will give a purple tint, (d) Vermilion may be used for red ink where neatness is required, as for title-lines of books. The quantity varies much, and necessitates care in its proportions.

It requires much soap to make it work clean, (e) For cheap work, such as posting-bills, red-lead may be used it requires additional soap to make it work clean, and its colour soon changes to black, (f) An excellent permanent red, of rich tone, may be produced from Indian red. (g) Venetian red is easily ground into a smooth ink, and requires but little more soap than the varnish usually contains; it is not very intense, (h) 2 oz. mineral orange-red, 1 oz. (Chinese vermilion; grind in printers' varnish or oil, as prepared for ordinary printing-ink.

Yellow

(a) The highest yellow is obtained from chromate of lead, which is easily ground into a fine ink, works freely and well, and requires but little soap beyond what the varnish contains. (6) Yellow ochre is easily ground into a fine ink; it gives a useful colour, dull, but permanent.