Classifications of Ink

[This is taken from David N. Carvalho's Forty Centuries of Ink, originally published in 1904, edited by D. J. McAdam.]


The inks used by us have nothing in common with those of the ancients except the color and gum, and mighty little of that.

Those of the “gall” class employed in the fourteenth, fifteenth, sixteenth, seventeenth and eighteenth centuries, some formulas of which are utilized by the manufacturers of ink in our own time, consisted generally in combination; infusions of nut-galls, sulphate of copper or iron, or both, and fish-glue or gum, slightly acidulated. The frequent introduction of the so-called “added” color into these inks, time has shown to have been a grave mistake.

The common acceptation of the term “ink” may be said to characterize an immense number of fluid compounds, the function of which in connection with a marking instrument is to delineate conventional signs, characters and letters as put together and commonly called writing, on paper or like substances.

To classify them would be impossible; but black writing ink, chemical writing fluid, colored writing ink, copying ink, India ink, secret or sympathetic ink, and indelible ink make seven classes; the others may be denominated under the head of miscellaneous inks, and of them all, there is no single ink answering every requirement and few answer at all times the same requirements.  Ink may be either a clear solution of any coloring matter or of coloring matter held in suspension.  It is a remarkable fact that although most inks are chemical compositions and many times made after the same formula, identical results cannot always be calculated or obtained. This is more particularly to be noted in the case of black writing inks otherwise known as the tanno-gallate of iron inks [gallic and gallotanic acid obtained from nut-galls, sulphate of iron, (green copperas) and some gummy vehicle].

The variations would appear to be largely due to the difference in quality of the gall-nuts, treatment, and temperature of the atmosphere; perhaps, however, not so much to-day as it was ten or twenty years ago, when to make ink of this character boiling processes were employed. Most of them as already stated are now “cold” made.

Inks of this class consist of a finely divided insoluble precipitate suspended in water by the use of gum and possessing a slight acidity.

The requisites of a good black writing ink or black writing fluid require it to flow readily from the pen, to indicate in a short time a black color and to penetrate the paper to an appreciable degree, and more important than all the rest, to be of great durability. When kept in a closed vessel no sediment of any account should be precipitated, although such will be the case in open ink-wells, and this the quicker the more the air is permitted to get to it. If it is to be used for record or documentary purposes it must not be altogether obliterated if brought into contact with water or alcohol, and should depend for permanency on its chemical and not on its pigmentary qualities.

The second class, called for distinction “chemical writing fluids,” possesses the same essential ingredients to be found in class one, but much less in quantity and with some “added” colored substance which I shall term “loading,” for its real purpose is to cheapen the cost of production and not altogether as some manufacturers state “simply to give them an agreeable color.”

Previous to the discovery of the soluble anilines, logwood, indigo, madder, orchil and other dyeing materials were used for a period of some eighty years and vanadium for some twenty years (very costly at that time), for this purpose, but since 1874, and with frequent changes as the newer aniline compounds were invented, these by-products of coal-tar, as well as logwood, etc., have been and are to-day employed for “loading,” or as the manufacturer expresses, it “added color.” The chemical writing fluids as now prepared, yield when first written a blue or green color with a tendency to change to black afterwards. They are not as permanent as those of the first class.

Another black ink not durable, however, is “logwood;” its extract is combined with a little chromate of potassium and boiled together in water. It possesses its own “gum” and contains some tannin. In combination with alum and water, it forms a dark purple ink.

The colored writing inks, of which “red” is the more important, are in great number and with hardly an exception at the present time, manufactured by adding water and water-glass to a soluble aniline red color. Cochineal which was used for red ink formerly is now almost obsolete. Nigrosine, one of the best known of them, is much used as a cheap “black” ink, but as it is blue black and never becomes black, it really belongs to the family of “colored” writing inks. They possess an undeserved popularity for they flow freely from the pen which they do not corrode, nor do they thicken or spoil in the inkwell; they are however very “fugitive” in character and should not be employed for record, legal, monetary or other documentary purposes. The indigo and prussian blue inks are well known, the former under certain conditions a very permanent ink, the latter soon disintegrating.

Copying inks are of two kinds, one dependent on the addition of glycerine, sugar, glucose or like compounds to the black writing inks or chemical writing fluids heretofore mentioned, which are thereby kept in a moist offsetting condition; the other due to the solubility of the pigmentary color with water, such as the aniline inks which are given more body than those for ordinary purposes—and the logwoods in which the pigment is developed and given copying qualities by chemicals, and hence becomes responsive to the application of a sheet of paper dampened with water. Copying ink should never be used for “record” purposes as it is affected by changes of the temperature.

India ink, sometimes called China ink, or as formerly known by the ancients and in classical and later times “Indian ink,” is now used more for drawing and engrossing than it is for commercial purposes. It belongs to the “carbon” class and in some form was the first one used in the very earliest times. In China it is applied with a brush or pith of some reed to the “rice” paper also there manufactured. It is easily washed away unless bichromate of ammonium or potassium in minute quantities be added to it, and then if the paper on which it appears be exposed for a short time to the action of the actinic rays of sunlight, this gummy compound will be rendered insoluble and cannot be removed with any fluid, chemical or otherwise.  It possesses also great advantages in drawing, since it acts as a paint, and will give any degree of blackness according to the quantity of water mixed with it.

Secret or sympathetic inks are invisible until the writing is subjected to a subsequent operation, such as warming or exposing to sunlight. To further aid the object in view, the paper may be first steeped in a liquid and the writing only made visible by using another liquid which has some chemical affinity with the previous one. The number of this kind were but few but have multiplied as chemistry progressed.  The ancients were acquainted with several modes.  Ovid indiscreetly advises the Roman wives and maidens if they intend to make their correspondence unreadable to the wrong persons to write with new milk, which when dried may be rendered visible by rubbing ashes upon it or a hot iron. Pliny suggests milky juices of certain plants of which there are a considerable variety.

Indelible ink is not used for writing purposes on paper, but is found best adapted for marking linen and cancellation or endorsing purposes. It is chiefly composed of nitrate of silver preparations, to which heat must be applied after it has been dried; or a pigment is commingled with the same vehicles used in making common printing ink and in its use treated as such.

Diamonds, gold, silver, platinum and a host of other materials are manufactured into ink and are to be placed under the head of miscellaneous inks. They are in great number and of no interest in respect to ink writing except for engrossing or illuminating.

Still another ink once held in much esteem and now almost obsolete is the so-called “safety” ink.

Manufacturers, chemists and laymen in great number for many years wasted money, time and energy in diligent worship at a secret shrine which could not give the information they sought. A summary of the meager and barren results they secured is of little value and unimportant. Hence, there is no REAL “safety” ink.

It is true that lampblack (carbon) as made into ink, resists any chemical or chemicals, but simple water applied on a soft sponge will soon remove such ink marks. The reason for this is obvious, the ink does not penetrate the paper.

“Safety” ink which will not respond to acids may be affected by alkalis, or if resisting them separately, will yield to them in combination.


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