B. There are several cheaper home-made 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 he 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. (b) 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 pulverized indigo. Boil the mixture until most of the water has evaporated ; then add 5 parts gum arable, 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 biehromate 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 them selves with such ink, make use of a dilute solution of bicbromate 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 into a leaden mould slightly oiled, or make it up iu any other convenient way. (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 arable, and then formed into cakes. (g) Mix finest lamp-black with a solution of 100 gr. lac and 20 gr. borax in 4 oz. water.
ink used by printers is compounded mainly of two ingredients, colouring matter and varnish. The former varies according to the quality and tint of the ink ; the latter may be obtained by natural resinous substances, or by mixing oil, rosin, and soap.
A. BLACK.—(a) The chief colouring matter in black printing-ink is vegetable lamp-black. The price of the best qualities precludes their use, except for specially fine ink ; nevertheless, good ink cannot be made with inferior samples. An undue proportion of lamp-black in the ink will cause it to smear, however long it may have been printed, and to "set-off" during book-binding opera tions. Thus the thickest inks are not the best, if the lamp-black is more than the varnish can bind. Ivory-black is too heavy to be used alone ; but a proportion ground up with the other ingredients makes a valuable ink for producing the best possible effect with wood-engravings.
Only the best and blackest is admissible. Prussian blue, ground exceedingly fine, and used
sparingly, deepens the colour of ink ; in excess, it gives a cold appearance. Indigo may replace Prussian blue. Perhaps the blackest tint is produced by equal quantities of each. To give a rich tone, and remove the coldness caused by indigo and Prussian blue, the addition of a little Indian red is strongly recommended.
The natural resinous substances employed as a source of varnish are balsam of copaiba and Canada balsam. The former is superior, and, when old and pure, may be used without any prepa ration. The latter is much thicker, and dries more quickly, and cannot therefore be used alone ; but for a strong ink, a small proportion may with advantage be added either to the balsam of copaiba or to the artificial varnish now to be described.
The basis of the artificial varnish is linseed-oil, which should be as old as possible. Of all other oils, the only one recommended as a substitute is nut-oil. The rosin used may be either black or amber. It melts in the boiling oil, and combines with it, preventing its separation from the colouring matter and staining of the paper, and binding the ink to prevent its smearing. The properties possessed by soap, which render it such an indispensable ingredient of printing-ink, are that it causes the ink (1) to adhere uniformly to the face of the type, (2) to coat it completely with the smallest quantity, (3) to leave the face of the type clean, and attach itself to the surface of the damp paper by the action of pressure, and that repeatedly, (4) to wash easily off the type, and (5) to never skin over, however long it may be kept. For all dark inks, well dried yellow or tur pentine soap may be employed ; for light-tinted inks, curd-soap is preferable. Used in excess, soap tends (1) to render the colour unequal, where a large surface is printed, (2) to spread over the edges of the types, so as to give them a rough appearance, and (3) to prevent the ink drying quickly, and cause it to " set off" when pressed. It is thus opposed to the binding quality of the rosin. Its due proportion is when the ink works clean, without clogging.
The combination of these several ingredients is effected in the following manner :—Into an iron vessel having 2-3 times the capacity of the materials it is to receive, put 6 qt. linseed-oil, and make a fire under it. After a time, the oil simmers and bubbles up, but as the temperature increases, the surface resumes placidity ; next it commences to smoke, and then to boil, emitting a very strong odour ; as the boiling continues, a scum arises. At this stage, repeated tests should be made to ascertain whether the escaping vapours will ignite. At the moment when they will do so, the pot is removed' from the fire, and placed on the ground, and the contents are stirred with an iron spatula, and kept burning. The pot is covered occasionally to extinguish the flame, while samples are withdrawn to test the consistence. When drops of the oil let fall upon a porcelain surface will draw out into strings about in. long, the oil is suited for ink for ordinary book-work. The flame is then extinguished by firmly replacing the cover. On removing it, there is a great escape of strong-smelling smoke, and much froth ; the latter is made to subside by thorough stirring, and when this is accomplished, but not before, 6 lb. of amber or black rosin is gradually introduced and stirred in. When the rosin is dissolved, 1 lb. of dry brown or turpentine soap, in slices, is stirred in gradually, and cautiously, as it froths copiously. When all the soap is in, and the frothing has ceased, the pot is returned to the fire till its contents boil, constant stirring being maintained. This completes the varnish. Into an earthenware pot, or a tub, of sufficient capacity, is put 5 oz. of Prussian blue, or indigo, or the two combined ; then 4 lb. of the best " mineral lamp black," and 3i lb. of good lampblack; next add the varnish by degrees, while warm, stirring meantime and until all the ingredients are thoroughly mixed ; finally pass it through a levigating mill, or between the stone and muller, and reduce it to impalpable fineness.