Common black writing-ink is the tannate of the sesquoxyd of iron mixed with a smaller quantity of the gallate of the sesquoxyd of iron. When in the liquid form, it is generally the tannate and gallate of the protoxyd; but after being long kept, (or put on the paper and drying there,) it absorbs more oxygen from the atmosphere; and thus the saline compounds become the per-tannate and per-gallate, which are blacker than the tannate and gallate of the protoxyd. It is thus and therefore that good modern ink is known by the simple test-quality of darkening by age. On the other hand, when writing becomes yellow, pale or indistinct by age, it is from the decay of the imperfectly combined vegetable astringent,—the marks on the paper or parchment being then little more than the stain of the per-oxyd (that is the sesquoxyd) of iron. If the written surface be then carefully washed or even moistened with the infusion of nut-galls, it will be rendered blacker, and if before indistinct will become legible. This may sometimes be better accomplished by first applying a weak solution of oxalic acid or very dilute muriatic (hydro-chloric) acid, and then delicately laying on the infusion of galls.
When the writing paper has been made of inferior rags, bleached with chlorine, the best ink used upon it is liable to become discolored.
Nut-gulls or gall-nuts (Gallæ-tinctoriæ) are excrescences growing upon the leaves or twigs of oak trees, (especially the Quercus infectoria,) caused by the puncture of an insect (the Cynips gallæ-tinctoriæ) which deposits its eggs in the perforations thus made. The Quercus infectoria is most abundant in Persia, Mesopotamia, Syria and Asia Minor, from which countries the galls are brought in large quantities to the manufactories of Europe and America. The best are called “Aleppo galls,” from the name of the Syrian city which is the chief original market for them. Those from Smyrna are also highly esteemed.
They contain the vegetable astringent principle called tannin in greater abundance than any other known substance. This is chemically resolved into the acids known as the tannic and gallic. All the woods and barks employed in the manufacture of leather by the tanning of hides contain this astringent matter in various degrees. The oak and the hemlock, for instance, are in extensive and familiar use for this purpose in the United States. The blackness of ink, as has been already indicated, is derived from the combination of these two acids with oxydized iron in saline compounds which are insoluble in water, and are therefore precipitated or deposited at the bottom of the fluid, unless held mechanically suspended in it, by gum, sugar or some similar substance which gives the quality of viscidity to its solutions.
The following will serve as a good formula for making common ink, and will be enough to give an idea of the ordinary and general mode of its composition:—“Take of Aleppo galls finely bruised, six ounces,—sulphate of iron, four ounces,—gum Arabic, four ounces,—water, six pints. Boil the galls in the water for about two hours, occasionally adding water to supply the loss from evaporation; then add the other ingredients; and keep the whole for two months in a wooden or glass vessel, which is to be shaken at intervals. Then strain the ink into glass bottles, adding a few drops of creosote to prevent mouldiness.”
Besides its property of viscidity, the gum possesses the power of preventing the ink from being too fluid: and it also serves to protect the vegetable matter from decomposition. The great desideratum or requisite is that the ink should flow with perfect freedom from the pen, to allow rapid writing, and that it should adhere to the paper, or “bite into it,” so as not to be effaceable by washing or sponging. The great defect to be avoided and prevented is the want of durability. The writing ink of the ancients was characterized by great permanency, being composed of finely pulverized carbon mixed with a mucilaginous or adhesive liquid. India or China Ink is of this composition: it is formed of lamp-black and size or fine animal glue, with the incidental addition of perfumes. It is used in China with a brush, both for writing and painting on Chinese paper; and it is employed in other countries for making drawings in black and white,—the different depths of shade being produced by varying the degree of dilution in water.
Inks of other colors than black were anciently used only for purposes of ornamental and decorative writing. In later and present times, red and blue inks have been extensively employed in ruling account-books and other paper for like uses. Blue ink, within ten or more years past, has been, with many, a preferred fluid for common writing.
Blue ink, when properly made, flows with great ease and rapidity from the pen, dries almost instantly on the paper, and has been supposed or expected to be quite durable, and unchangeable in color, under ordinary vicissitudes. Yet, experience has demonstrated the contrary,—though various and well-contrived chemical combinations have been attempted for the purpose. Blue inks that change to black some time after writing are very popular. On well-made and high-priced paper, and with gold pens, such inks, if prepared by good chemists, may ultimately prove worthy of the high esteem in which they are held; but their absolute and unchangeable durability is yet to be tested by experience, before they can be safely employed for writings of permanent value, and relied on for use in making records designed for preservation and reference during a long course of years.
There is a compound of bichromate of potash and extract of logwood, which forms a very cheap and convenient writing fluid. Dr. Ure pronounces it “a vile dye.” Yet it may have its utilities, in localities remote from the centres of civilization and commerce,—as in the new settlements in western America, in Australia, &c., and for travelers in Africa, in the Arctic and other barbarous or uninhabited regions. The following is the best formula which can be given for this compound; and we present it on the highest chemical authority:—“Take Bichromate of potash, 1-4 oz.—Extract of logwood 1 oz.—Boiling water, 1 gallon.”
We have taken the trouble to give this prescription or formula, because some quacks have been peddling it all over the country, at all sorts of prices, varying (according to the credulity and liberality of purchasers) from 50 cents to $250. We give it for just what it is worth; and that is—exactly what this book costs the reader.