Ink, the name given to a variety of preparations designed for producing colored letters in writing or printing. IN of the ancients appears to have been similar to the solid Chinese or India ink - a combination of lampblack with glue or gum, in the proportions, as given by Dioscorides, of three parts of the former to one of the latter. The liquor of the cuttle fish is also said by Cicero and Pliny to have been in use for ink. These preparations were used in a fluid state, by means of a style with a split point. Manuscripts written from the 5th to the 12th century are generally very legible, while those of the 15th and 16th centuries are made out with difficulty in consequence of the discoloration of the ink. This is owing in the one case to the permanent quality of the ancient inks, which were of the nature of a black paint, and also to the use of parchment and of a porous paper of cotton rags which absorbed the ink; and in the other to the closer quality of the linen paper of the later period, and the changeable nature of the ink, which was in fact a dye prepared from nutgalls and sulphate of iron. Paper bleached with excess of chlorine would cause, this kind of ink to be discolored.

The decay of the vegetable portion of the ink would cause the color to fade, and ancient writings thus rendered illegible have been restored by careful application of an infusion of galls. In an essay on the "Origin and Progress of Printing," privately printed by the Philobiblon society in England, 1859, it is said: "The ink of the ancients, and that used in the middle ages, had a consistency much thicker than that at present in use; very highly gummed when applied to papyrus, parchment, or paper, it formed letters in relief, as if they were embossed, which has given rise to an erroneous conjecture that these writings were produced by a sort of typographic process. Black ink was in general used for manuscripts and charters. The basis of all the black inks was carbon in various forms, as lampblack. Red ink was generally employed for writing initials and the titles of books and chapters; hence the term rubrics, from rubrica, red. At Orleans there is a charter of Philip I., dated 1090, written in green ink. The emperors signed in purple ink obtained from the murex; gold and silver inks were chiefly employed on colored parchments or purple vellum.

The celebrated codex of Upsal is written with silver ink upon violet parchment, the initials and some passages being in gold." - Though the same materials were used for several centuries that are now employed for the best inks, little was known of the real nature of the compounds produced until the researches of Dr. Lewis and of Ribau-court toward the close of the last century; the latter published an interesting paper containing an account of his observations in the Annales de chimie of 1798. The inks from that time were improved; but the recipes have until recently been objectionable from the introduction of unnecessary ingredients, and particularly from the necessity of employing much gum to prevent the coloring matter from subsiding; this renders the ink thick and indisposed to flow freely from the pen, and also liable to become mouldy. The requisites of a good writing ink are permanency of character, close adherence to the paper, a good color, no tendency to mould, and a proper consistency.

A combination of nutgalls with sulphate of iron was long the only suitable black solution known. The galls contain four vegetable substances, viz., gallic and tannic acids, mucilage, and extractive matter. The acids are regarded as more particularly necessary to a good ink, forming with the oxide of iron of the copperas a tanno-gallate of iron. Of the three causes of the deterioration of ink - mouldiness, the separation of the black coloring matter, and the change of color - Dr. Bostock, in an able paper in the "Transactions of the Society of Arts " for 1830, attributes the first to the mucilage, the second to the extractive matter, and the third to the tannin, which is disposed to decompose and thus involve the destruction of the compound of which it is an ingredient. The more nearly the ink approaches the composition of a gallate of iron, the more permanent he regards it. Several of the recipes require long exposure of the decoction of galls to the air, after this is obtained by boiling in water, the effect of which is to convert much of the tannin into gallic acid.

Dr. Bostock recommends that the galls should be macerated for some hours in hot water, and the fluid filtered; the filtrate should then be exposed for two weeks to a warm atmosphere, when any fungoid growth that forms must be removed; and the infusion being made stronger than usually directed, no addition of mucilaginous substance will be required to give it a proper consistency. The solution of sulphate of iron should also be boiled or exposed some time to the air, which causes a portion of sesquioxide of iron to be formed, the presence of which is advantageous. The recipes for this class of ink alone are very numerous. That of Booth for a fine black ink is: Aleppo galls 12 lbs., sulphate of iron 4 lbs., gum arabic 3 1/2 lbs., water 18 gallons; the bruised galls to be exhausted by three successive boilings, each time with a reduced quantity of water; the decoction is strained, and while warm the solution of gum and copperas, also warm, is to be added, and the mixture is left for several weeks to deposit its sediment. A few drops of creosote added will prevent mouldiness. - Among the other kinds of ink, the following appear particularly worthy of notice.

The blue ink first introduced by Mr. Henry Stephens of London, remarkable for a blue color which, soon after drying changes to deep black, for perfect fluidity, and tenacious adherence to the paper, is a tanno-gallate of iron dissolved in sulphate of indigo, the coloring matter thus not being suspended as in the ordinary inks, but in complete solution. Another variety, also invented by Mr. Stephens, and remarkable for its tendency to fade by continued exposure to light, and to recover its hue when excluded from it, is made by submitting Prussian blue for two days or longer to the action of strong nitric or hydrochloric acid, then washing it well with water till all acid is removed, and finally dissolving it in oxalic acid. Hornung's recipe is to mix 4 parts of solution of perchloride of iron with 750 parts of water, and precipitate with 4 parts of cyanide of potassium in solution; the precipitate collected is washed with several additions of water, and allowed to drain until it weighs about 200 parts; it is then dissolved in one part of oxalic acid.

Runge's ink, remarkable for its clearness and fitness for steel pens, which it does not corrode, is a cheap composition prepared by gradually adding one part of solution of chromate of potash to 1,000 parts of a strong cold decoction of logwood, 22 lbs. of logwood being boiled down with water to 14 gallons. The ink thus made is very black, and is not affected by weak acids, nor can it bo washed out with water. It is, however, liable to become viscid and gelatinous. Dr. Normandy's indelible writing ink, which is remarkably permanent, is made by grinding 24 lbs. of Frankfort black with mucilage obtained by adding 20 lbs. of gum to 60 gallons of water, straining through a coarse flannel, then adding 4 lbs. of oxalic acid, and as much decoction of cochineal and sulphate of indigo as will give the required shade. Berzelius invented an ink which he regarded as the best writing ink known, and also nearly indelible; it is vana-dic acid combined with ammonia and mixed with infusion of galls. - Copying inks, which are intended to give an impression of the writing made with them to a second or a third sheet moistened and pressed upon the original, are the ferro-gallic inks with a larger proportion of gum than they usually contain, and a portion besides of sugar or of sugar candy. - Red ink may be made by the recipe of Heusler, which is to boil 2 oz. of Brazil wood, 1/2 oz. alum, and the same of crystals of tartar, in 16 oz. of pure water, till the water is reduced one half; in the strained liquor 1/2 oz. of gum arabic is to be dissolved, and a tincture added made by digesting 1 1/2 dram of cochineal in 14 oz. of alcohol of specific gravity 0.839. Booth employs Brazil wood 2 oz., chloride of tin 1/2 dram, gum arabic 1 dram, water 32 oz., and boils the whole down to 16 oz.

Various recipes may be found for different colored inks, but there is little use for them. They are generally composed of coloring matter held in suspension by thickening the liquid with gum arabic. The nature of the Chinese or India ink has been already noticed. Proust says that lampblack purified by potash lye and mixed with a solution of refined glue, moulded and dried, makes a quality of this ink preferred by artists even to that of China. Until some recent discoveries it was supposed that this ink used with acidulated water was inattackable by chemical reagents that were not destructive to the paper. - The so-called indelible or marking inks were formerly altogether made by dissolving nitrate of silver in water and adding gum arabic and sap green, and were used in connection with a pounce, which was first applied to the linen on the spot to be marked. The pounce was an aqueous solution of carbonate of soda to which gum arabic was added. The best marking inks are now made by combining the two preparations at once, and bringing out the color after the application to the cloth by exposure to heat.

A good ink is made by dissolving 7 parts of carbonate of soda in 12 of water, and adding 5 parts of gum arabic, then mixing with this 5 parts of nitrate of silver liquefied in 10 of ammonia; the mixture is to be gradually heated to ebullition in a flask, when it becomes very dark and of the proper consistence. Tartaric acid is sometimes advantageously employed to produce tartrate of silver, as by the following process: nitrate of silver is triturated in a mortar with an equivalent of desiccated tartaric acid; water added causes crystals of tartrate of silver to separate with liberation of nitric acid; this is neutralized by careful addition of ammonia, which also dissolves the tartrate of silver; the preparation is then thickened with gum, and coloring matter is added at pleasure. The Italian marking ink is terchloride of gold applied to cloth moistened with solution of chloride of tin. The subject of indelible inks will be further treated under Nitrates. - Sympathetic inks are preparations which when used for writing leave no visible, or at least only colorless, marks upon the paper. These are afterward brought out in colors by exposure to heat or to moisture, or by application of other substances.

By the ancients it was known that new milk or the milky sap of plants might be so used, the writing with it being made visible by dusting over it a black powder. The property of writing made with the solution of acetate of lead to turn black by application of gaseous or liquid sulphuretted hydrogen was known in the 17th century, and ascribed to magnetic influences. The action was afterward styled sympathetic, and the name has continued to be applied to the various preparations of this nature. The materials of the common ferro-gallic inks may be used separately for a sympathetic ink, the writing being done with the sulphate of iron solution and washed over with that of the galls, as the writing of some old manuscripts is now occasionally restored. A dilute solution of chloride of copper used for writing is invisible until the paper is heated, when the letters are seen of a beautiful yellow, disappearing with the heat that developed them. The salts of cobalt, as the acetate, sulphate, nitrate, and chloride, possess a similar property, the letters appearing blue. The addition of a salt of nickel renders them green. The magic or chemical landscapes are made by the use of these metallic salts.

The sky being painted with salt of cobalt alone, and foliage with the same mixed with nickel, the application of heat brings them out in their appropriate colors. A winter landscape, with the bare trees and ground covered with snow, may thus by accession of warmth be clothed with the green hues of summer. - Lithographers employ an ink for tracing designs on paper, which are to be transferred to stone, composed of shell lac 1 1/2 oz., soap 2 oz., white wax 3 oz., tallow 1 oz., a strong solution of gum sandarach 3 tablespoonfuls, and lampblack; also an ink for taking impressions from engraved plates, which are to be transferred to stone, composed of tallow, wax, and soap, each 4 oz., shell lac 3 oz., gum mastic 2 1/2 oz., black pitch 1 1/2 oz and lampblack. - Printing ink is a preparation very different from any of the inks used for other purposes; and its manufacture demands no little skill and experience. It should be of a soft adhesive character, readily attaching itself to the surface of the types, and as easily transferred to the paper pressed upon them, conveying in a clear tint the exact stamp.

Thus spread in a thin film and pressed into the paper, it should quickly dry, and at the same time be so incorporated with the paper as not to be removable by mechanical means, while its composition insures for it durability and a power to resist the action of chemical agents as well as atmospheric influences. While disposed to dry readily on being applied to paper, it should retain its softness in the mass and while excluded from the air, and in this condition undergo no change. Its ingredients must not be of a corrosive nature to injure the rollers employed in spreading it. The appearance of good ink is glossy and somewhat oily; its texture smooth without grains; and its tenacity such as to cause it to adhere to the finger pressed against it, and yet leave but a short thread suspended from a portion taken out. The usual materials employed in its manufacture are linseed oil, rosin, and coloring matters. Rosin oil is largely used for some of the cheaper inks. For the best inks the linseed oil is selected of the purest quality, and this is clarified by digesting it for some hours with dilute sulphuric acid at a temperature of 212°, and then washing it with hot water; it will then dry much more quickly.

The oil is then boiled, and the inflammable vapors that rise are ignited, and when they have burned a few minutes a cover is placed over the vessel, extinguishing the flame. The boiling is not stopped until a drop taken out and placed on a cold surface is covered with a film as it cools. A portion of rosin is then dissolved in the oil, the quantity depending on the degree of stiffness the ink may require; that for books and strong, stiff paper bearing more rosin, and receiving in consequence more gloss, than the ink for newspapers. The degree of viscidity given to the oil should also have reference to the use required of the ink. For letterpress printing soap should be added to the materials to enable the ink to be taken up clearly from the types without smearing. The best kind is yellow rosin soap, cut up into slices, dried, reduced to powder, and incorporated with the oil and rosin, or varnish, and before mixing placed again over the fire to expel any remaining moisture. Lampblack is almost universally employed as the coloring matter; and much care is given in the manufacture of this article to obtain it of the very best quality. Other carbonaceous blacks reduced to impalpable powder are sometimes employed. For colored inks various pigments are introduced instead.

The mixture is made with the hot compound of burnt oil and rosin in a cylindrical vessel, in which a revolving shaft with arms serves as a stirrer. From this the ink is drawn off, and is then ground in a mill until the ingredients are thoroughly incorporated. Various recipes may be found in Ure's "Dictionary" and Mus-pratt's "Chemistry " for printing inks of other materials than the above. For ancient processes see the work of Caneparius, De Atra-mentis cujuscumque Generis (Rotterdam, 1718).