INK, Printers'. This is a very singular composition, much of the na ture of an oil varnish, but differing from it in the quality of adhering firmly to moistened paper, and in being, to a consi derable degree, soluble in soap-water.
It is, when used by the printers, of the consistence of rather thin jelly, so that it may be smeared over the types readily and thinly, when applied by leather cushions, and it dries very speedily on the paper without running through to the other side, or passing the limits of the letter.
The method of making printers' ink is thus described by Dr. Lewis. Ten or twelve gallons of nut-oil are set over the fire in a large iron pot, and brought to boil. It is then stirred with an iron ladle, and, whilst boiling, the inflammable va pour rising from it either takes fire of it self, or is kindled, and suffered to burn in this way for about half an hour, the pot being partially covered so as to regulate the body of the flame, and consequently the heat communicated to the oil. It is frequently stirred during this time, that the whole may be heated equally, other wise a part would be charred and the rest left imperfect. The flame is then extin guished by entirely covering the pot. The oil by this process has much of its unctuous quality destroyed, and when cold is of the consistence of soft turpen tine, and is then called varnish. After this it is made into ink by mixture with the requisite quantity of lamp-black, of which about two ounces and a half are sufficient for sixteen ounces of the pre pared oil. The oil loses by the boiling about an eighth of its weight, and emits very offensive fumes. Several other addi tions are made to the oil during the boil ing, such as crusts of bread, onions, and sometimes turpentine. These are kept secret by the preparers. The intention of them is more effectually to destroy part of the unctuous quality of the oil, to give it more body, to enable it to adhere better to the wetted paler, and to spread on the types neatly and uniformly.
Besides these additions others are made by the printers, of which the most important is generally understood to be a little fine indigo in powder, to improve the beauty of the colour.
Red printers' ink is made, by adding to the varnish about half its weight of ver milion. A little carmine also improves the colour. (Encycl. Arts & Metiers, vol. iii. p. 518.) bras, coloured. Few of these are used except red ink. The preparation of these is very simple, consisting either of decoc tions of the different colouring or dyeing materials in water, and thickened with gum-arabic, or of coloured metallic ox ides, or insoluble powders, merely diffus ed in gum-water. The proportion of gum•arabic to be used may be the same as for black writing ink. All that applies to the fixed or fugitive nature of the se veral articles used in dyeing may be ap plied, in general, to the use of the same substance as inks.
fax, red, is usually made by boiling about two ounces of Brazil wood in a pint of water for a quarter of an hour, and adding to the decoction the requisite quantity of gum, and about half as much alum. The alum both heightens the co lour and makes it less fugitive. Proba bly a little madder would make it more durable.
lxx, blue, may be made by diffusing Prussian blue or indigo through strong gum-water.
km, yellow, may be made by a solution of gamboge in gum-water.
Most of the common water-colour cakes, diffused in water, will make suffi ciently good coloured inks for most pur poses.
Inks of other colours may be made from a strong decoction of the ingredi ents used in dyeing, mixed with a little alum and gum•arabic. For example, a strong decoction of Brazil wood, with as much alum as it can dissolve, and a little gum, forms a good red ink. These pro cesses consist in forming a lake, and re. tarding its precipitation by the gum. See