The peculiar ink employed by draughtsmen is termed "Indian," because the best qualities have always come to us from India and China. In the latter country the manufacture of drawing-inks is a large industry, and several factories are to be found in Shanghae and other parts of the empire.
A. The Chinese mode of manufacture is as follows: - In some parts of N. China, the lampblack, which forms the foundation of the ink, is prepared much in the same manner as in Europe. In other districts the following method prevails: - The furnaces are built upon the ground, with a length varying from 8 ft. to 40 ft., or even 50 ft., and with a mouth about 2 ft. in diameter. The material generally used is pine, or other resinous wood, or the resin itself, which is burned at the mouth of the furnace. Only the black deposited at the extreme end of the furnace is used for the finest ink, all the remainder being proportionately coarser. The fineness of the grain depends also upon the slowness of the combustion. The very finest black is said to be derived from pork-fat; the next from oils and other kinds of grease. The smoothness of the ink is likewise largely dependent upon the careful sifting of the black through silken bags or sieves. The first operation in compounding the ink is to soak a quantity of the excellent glue made from buffalo-hide; when thoroughly swollen, it is set aside, and will keep in this state for several days. For use, the glue is melted in an iron pot, and as much lampblack is added as will produce a soft paste. This paste is very carefully kneaded by hand.
A small quantity of pea-oil is then added, and the whole is maintained at a temperature of 130° to 140° F. (54° to 60oC), until the paste is found to be perfectly homogeneous. It is then poured out in the form of flat cakes, weighing 1 lb. to 2 lb. each, and is left in that condition for many days to "ripen." It often happens, when the weather is hot and damp, that the cakes become covered with mould; but this does not seem to produce any ill effect. While one set of workmen manufacture the paste, another set fashion it into the familiar forms met with in commerce. The latter sit at a bench, with a small brazier beneath; the workman warms a piece of the paste, kneads it vigorously in his hands, presses it into a mould, and places the latter under a long lever, on the end of which he sits, so as to compress the ink forcibly for some seconds; he fills another mould in the meantime, and so the operation progresses. The moulds are made of wood, the characters to be impressed upon the cakes being engraved also on wooden dies. One of these dies is dropped into a cavity in the bottom of the mould, while another is laid on the top of the paste in the mould.
Common qualities are often pressed into large moulds with several partitions, so that the cakes, when dry, can easily be broken off from each other. For wholesale manufacturing purposes, the best is simply rolled, and the sticks, perforated at one end, are strung together in bunches of 1/2doz. to 1 doz. The drying of the cakes occupies 5 to 6 days, according to the temperature. Their high polish is due to brushing over with a hard brush impregnated with tree-wax (probably that secreted by Coccus Pe-la, on the branches of Fraxinus chinensis), which has the additional effect of preventing the ink soiling the hands when they are moist. The peculiar odour possessed by the finest ink is produced by mixing a small quantity of musk, or of Borneo camphor, with the paste while hot. The common qualities are unscented. The Japanese make ink in the same way, but it is inferior to the Chinese product, as, though the glue and gelatine are equally good, less care is taken in the preparation of the lamp-black. The finest ink should be slightly brown in tint; when quite black, bluish, or grey, it is inferior. A stick of fine ink gives a clear, sharp sound when struck; if the tone be dull, the ink 4s not homogeneous. The heaviest ink is the best; it improves in colour and brilliancy by age.
The chief test of good ink is that it will produce a tint of any depth, without the slightest appearance of irregularity. Some cakes are worth 5s. to 6s. each.
B. There are several cheaper homemade imitations of the Chinese ink, besides some recipes for improving the qualities of the latter. They are chiefly as follows: - (a) To improve Indian ink for drawing, so that even the thickest lines will quickly dry, add 1 part of carbolic acid to 80 of the ink. If, by mistake, too much has been added, it may be rectified by putting in more Indian ink. If the mixture is properly performed, the ink is as easy to draw with as it is without carbolic acid, but dries quickly, and may even be varnished without discharging. (6) For making a deep-black Indian ink, which will also give neutral tints in its half shades, rub thoroughly together 8 parts lamp-black, 64 parts water, and 4 parts finely-pulverised indigo. Boil the mixture until most of the water has evaporated; then add 5 parts gum-arabic, 2 parts glue, and 1 part extract of chicory. Boil the mixture again till it has thickened to a paste;. then shape it in wooden moulds which have been rubbed with olive or almond oil. (c) Most of the black Indian ink met with in commerce possesses the disadvantage that it blots when a damp brush is passed over it; or, as draughtsmen say, "it does not stand." The addition of alum does but little good; but bichromate of potash accomplishes the object by rendering insoluble the glue which the ink contains, and thus making the ink permanent.
The bichromate of potash possesses a deep yellow (almost red) colour, but does not at all injure the shade of the ink, as 1 per cent, of it in a very fine powder, intimately mixed with the ink, is sufficient. The bichromate must always be mixed with the ink in a dry state, otherwise the latter might lose its friability in water. A drawing which has been made with this ink in the dark, or by artificial light, must be exposed to sunlight for a few minutes, which renders the bichromated glue insoluble in water. Draughtsmen who cannot provide themselves with such ink, make use of a dilute solution of bichromate of potash in rubbing up the ink. There is no danger of the yellow penetrating the paper if the ink is thick enough, (d) A substance much of the same nature and applicable to the same purpose as Indian ink may be formed in the following manner: - Convert 3 oz. isinglass into size by dissolving it over a fire in 6 oz. soft water; dissolve 1 oz. Spanish liquorice in 2 oz. soft water in another vessel over a fire; grind up on a slab with a heavy muller, 1 oz. ivory-black with the liquorice mixture; add this compound to the isinglass size while hot, and stir well together till thoroughly incorporated.
Evaporate away the water, and then cast the remaining composition in a leaden mould slightly oiled, or make it up in any other convenient way. This composition will be found quite as good as the genuine article. The isinglass size mixed with the colours work well with the brush. The liquorice renders it easily dissolvable on the rubbing up with water, to which the isinglass alone would be somewhat reluctant; it also prevents it cracking and peeling off from the ground on which it is laid, (e) Dissolve horn shavings with caustic alkali; boil the brown liquid in an iron kettle till it is thick; pour on double its weight of boiling water, and precipitate by dissolved alum; dry, grind, mix it with gum-water, and pour it into a mould; add perfume if desired. (f) Horse-beans, perfectly calcined, are ground to a fine powder, made into a paste with solution of gum-arabic, and then formed into cakes, (g) Mix finest lampblack with a solution of 100 gr. lac and 20 gr. borax in 4 oz. water, (h) Grind the finest lampblack to a paste with very weak solution of potash. It is then diffused through water rendered slightly alkaline; collected, washed with clean water, and dried.
The dry powder is levigated to a smooth, stiff paste with a strong filtered decoction of carrageen (Irish moss), or of quince seed. A few drops of essence of musk, and about half as much essence of ambergris, is added by way of perfume towards the end of the operation; after which it is moulded into cakes, and ornamented with Chinese characters and devices as soon as they are dry and hard. (i) A good Indian ink may be made from the fine soot from the flame of a lamp or candle, received and collected by holding a plate over it. Mix this with the size of parchment, and it will be found to give a good deep colour. Burnt rice has been by some considered a principal ingredient in the genuine Indian ink, with the addition of perfumes or other substances not essential to its qualities as an ink. (j) Dr. Precht gives an easy method for rendering drawings in Indian ink insensible to water, and thus preventing the ink from running when the drawing has to be coloured and the lines are very thick. To the water in which the ink has to be rubbed is added a weak solution of potash bichromate of about 2 per cent.
The animal gum contained in the Indian ink combines with the bichrome, and becomes insoluble under the influence of light. (A) Dr. Aug. Chevreuse has discovered that when the common cockchafer (Melo-lontha vulgaris) is decapitated an hour after feeding, each insect yields 4 or 5 drops of colouring matter, varying in hue with the leaves that have served as food. Dr. Chevreuse has thus obtained 14 different tints. Nichles, professor of chemistry, Preclaire, professor of design, and Chatelain, architect, report that the colour may be used for mechanical and other drawings in place of Indian ink, sepia, etc, and that it is unaffected by exposure to the light or admixture with water-colours. The fluid is collected on strips of glass or shells. For use it is only necessary to dissolve it in water. Laid on in a thick coat, it serves as a varnish. Two or three insects supply colouring matter sufficient, when suitably diluted with water, for the execution of a small landscape. (Bull, des Sci. et Arts de Poligny.) (l) Calcined lampblack, 100 oz.; boghead shale black, in impalpable powder, 50 oz.; indigo carmine, in cakes, 10 oz.; carmine lake, 5 oz.; gum-arabic (first quality), 10 oz.; purified oxgall, 20 oz.; alcoholic extract of musk, 5 oz.
The gum is dissolved in 50 to 60 oz. of pure water, and the solution is filtered through a cloth. The indigo carmine, lake, lampblack, and shale black, are incorporated with this liquor, and the whole is ground upon a slab with a muller in the same manner as ordinary colours; but in this case the grinding takes much longer. When the paste is thoroughly homogeneous, the oxgall is gradually added, and then the alcoholic extract of musk. The more the black is ground the fin6r it is. The black is then allowed to dry in the air, until it has acquired sufficient consistency to be moulded into cakes, which in their turn are still further dried in the air, out of the reach of dust. When quite firm, these cakes are compressed in bronze moulds, haring appropriate designs engraved upon them. The moulded ink is then wrapped in tinfoil, with a second envelope of gilt paper. The ink which has been prepared in this manner possesses all the properties of the real Chinese article. Its grain is smooth, it flows very well, mixes perfectly with many other colours, and becomes so firmly fixed to the paper, that other colours may be spread over it without washing it out. (Riffault.)