The quality required of a copying-ink is that it shall afford one or more copies of the written matter by applying dry or damped paper to its surface, and subjecting it to more or less pressure. The best kinds of copying-ink are usually prepared by adding a little alum to an extract of logwood of 10° B. (1.075 sp. gr.), or to a decoction of the same, and then, to improve its copying power, some sugar and glycerine or table-salt is added. Such inks have a violet tint, are purple when first written, and gradually darken on the paper. The copies taken from them are at first very pale, and only slowly darken. The chief recipes for copying-inks are the following: - (a) Mix about 3 pints of jet-black writing-ink and 1 pint glycerine. This, if used on glazed paper, will not dry for hours, and will yield one or two fair, neat, dry copies, by simple pressure of the hand in any good letter copy-book. The writing should not be excessively fine, nor the strokes uneven or heavy. To prevent "setting-off," the leaves after copying should be removed by blotting-paper. The copies and the originals are neater than when water is used, (b) A good copying-ink may be made from common violet writing-ink by the addition of 6 parts glycerine to 8 parts of the ink.
Using only 5 parts of glycerine to 8 of the ink, the ink will copy well 15 minutes after it has been used. With fine white copying-paper, it will copy well without the use of a press, (c) 1/2 lb. extract of logwood, 2 oz. alum, 4 dr. blue vitriol (sulphate of copper), 4 dr. green vitriol (sulphate of iron), 1 oz. sugar; boil these ingredients with 4 parts water, filter the decoction through flannel; add a solution of 4 dr. neutral chromate of potash in 4 oz. water, and a solution of 2 oz. "chemick blue" in 2 oz. glycerine. The " chemick blue " is the solution of indigo in sulphuric acid, or sulphindigotic acid, (d) A black copying-ink, which flows easily from the pen, and will give very sharp copies without the aid of a press, can be prepared thus: - 1 oz. coarsely-broken extract of logwood and 2 dr. crystallised carbonate of soda are placed in a porcelain capsule with 8 oz. distilled water, and heated until the solution is of a deep red colour, and all the extract is dissolved. The capsule is then taken from the fire. Stir well into the mixture 1 oz. glycerine (sp. gr. 1.25), 15 gr. neutral chromate of potash, dissolved in a little water, and 2 dr. finely-pulverised gum-arabic, which may be previously dissolved in a little hot water so as to produce a mucilaginous solution.
The ink is now complete and ready for use. In well-closed bottles it may be kept for a long time without getting mouldy, and, however old it may be, it will allow copies of writing to be taken without the aid of a press. It does not attack steel pens. This ink cannot be used with a copying-press. Its impression is taken on thin moistened copying-paper, at the back of which is placed a sheet of writing-paper, (e) A new kind of Parisian copying-ink has been recently introduced into Germany, which differs from those previously in .use in having, while liquid, a more or less yellowish-red colour; but on paper it rapidly turns blue, and immediately produces a distinct blue-black copying-ink; moreover, it remains liquid a long time, while ordinary violet copying-ink soon gets thick. This kind copies easily and perfectly. The following is the method of its manufacture: - A logwood extract of 10° B. (sp. gr. 1-075) has added to it 1 per cent, of alum, and then enough lime-water to form a permanent precipitate. This mass is then treated with a few drops of a dilute solution of chloride of lime (bleaching-powder), just enough being added to impart to it a distinct blue-black colour, after which dilute hydrochloric acid is added drop by drop until a distinctly red-coloured solution is produced.
To this solution is added a little gum, and 1 to 1 1/2 per cent, of glycerine. It is evident that the small quantity of chloride of calcium formed by this process greatly increases the copying power of the ink; while the exceedingly slight excess of free hydrochloric acid causes the ink to remain liquid, by holding in solution the lime and alumina lakes of logwood. When the writing dries, the acid gradually escapes, or is neutralised by the trace of alkali in the paper, so that the blue-black lake is left. It is evident that any considerable excess of hydrochloric acid must be avoided, as also the use of too much chloride of lime solution. (f) Add 1 oz. lump-sugar or sugar-candy to 1 1/2 pint good black ink; dissolve. (g) A decoction of Brazil-wood and glycerine used as an ink requires neither press nor copying-paper for multiplying the impressions; it is only necessary to lay tissue-paper upon the writing and to rub with the finger. (A) 5 1/2oz. best galls, 1 dr. bruised cloves, 40 oz. cold water, 1 1/2 oz. pure sulphate of iron, 35 minims pure sulphuric acid, 1/4 oz. sulphate of indigo in thin paste, and neutral or' nearly so. Place the galls, when bruised, with the cloves in a 50-oz. bottle, pour in the water, and digest, shaking daily, for a fortnight.
Filter through paper into another 50-oz. bottle. From the refuse of the galls wring out the remaining liquor through a strong elean linen or cotton cloth into the filter to avoid waste. Put in the iron, dissolve completely, and filter through paper. Add the acid, and agitate briskly; add the indigo, and shake up thoroughly; pass the whole through filter-paper. Filter from one bottle to another till the operation is complete. The same ingredients may be used for common writing-ink, reducing the proportion of galls to 4 1/2oz. (t) 1 lb. Aleppo nut-galls, bruised,; 1/2 lb. sulphate of iron (copperas), pounded; 1/4 lb. gum-arabic, pounded; 1/2 lb. white sugar-candy, pounded; 1 gal. water. Put the above into an earthenware bottle, and keep about " new milk " warm for a week; a few cloves will prevent "moulding." Cost to make a gallon, about 2s. &d. The bottle should have a good shaking three or four times a day. (f) Gum, 1/2 oz.; Spanish liquorice, 20 gr.; in 13 dr. of water, and add to it 1 dr. of lampblack, with a teaspoonful of sherry.