Scientific American, 14.8.1869
By Dr. Belmann.
The following are a number of formulae for preparing indelible ink to be made use of in marking linen. As they have all been thoroughly well-tried, and found effectual, it is to be hoped they may prove of some use to the public.
The linen is first moistened with a fluid, consisting of a mixture of, 2 parts carbonate of soda in crystals, 2 parts gum-arabic, 8 parts of water, and then dried. When quite dry, it is rubbed with a glass cloth to render it as smooth as possible, so that it may be easier to write upon. The composition of the ink itself is as follows: 1 2/3 pts. nitrate of silver, 16 pts. distilled water, 2 pts. gum-arabic, and 1/8 pt. of sap green. The nitrate of silver is first disolved in the distilled water, and the gum-arabic and sap green are subsequently added.
It is necessary to write with a quill pen, all metallic pens except gold ones, decomposing the ink. It is a good plan to trace the letters on the linen with a pencil before writing them.
Marking linen is most conveniently effected by using a pencil and a small copper plate with perforations corresponfing to the letters required. This plate is laid upon the linen, and the ink is applied with the pencil to the cut-out spaces, so that these spaces, and these alone are smeared with the ink.
The following ink is of service for marking linen with a pencil, when a metallic pattern-tracer is employed: 2 pts. Nitrate of silver, 4 pts. distilled water, 2½ pts. gum-arabic, 3 pts. carbonate of soda crystals, 5 pts. liquid ammonia.
The best way to prepare the ink is to first dissolve the nitrate of silver in the liquid ammonia, and the gum-arabic and soda in the distilled water. The two solutions are then mixed together and slightly warmed, when the whole mixture becomes brown. A few drops of a solution of magenta, makes the ink somewhat more distinct. It is of course unnecessary in this method to previously moisten the spot with gum-arabic solution.
For very fine linen the following ink is best employed: 4 pts. Nitrate of silver, 24 pts. distilled water. To this solution liquid ammonia is added, until the precipitate which is first formed, is re-dissolved. Then a little sap green, indigo, etc., are ground together, and dissolved in a solution of 4 pts. gum-arabic, and this so[l]ution and that of the nitrate of silver are mixed together. The whole is then diluted untill it occupies 32 parts. This ink is very limpid, and easy to write with.
When dry a hot iron need only be passed over the surface of the linen, when the letters will at once make their appearance, their tint being a deep black. The ink does not injuriously affect even the finest linen.
The discovery of an aniline black has led to the employment of this coloring matter in marking linen.
This ink has the advantage of being cheaper than the ink prepared from nitrate of silver. It has also another advantage over the latter salt, viz. that is it chemically indelible. The ink made with nitrate of silver can be removed by washing the linen with a solution of hyposulphite of soda, or by moistening it with a solution of bichloride of copper and then washing with liquid ammonia. This is not the case with the aniline ink, the color of which cannot be removed by any chemical agent whatever. Linen therefore marked with this ink can never be appropriated by other persons than the rightful owner.
Such aniline ink may be prepared in the following way: 8½ grs. of Bichloride of copper are dissolved in 30 grains of distilled water, then are added 10 grains of common salt, and 9½ grain of liquid ammonia. A solution of 30 grains of hydrochlorate of aniline in 20 grains of distilled water is then added to 20 grains of a solution of gum-arabic, containing 2 pts. water, 1 pt. gum-arabic, and lastly 10 grs. of glycerin. Four parts of the aniline solution thus prepared are mixed with one part of the copper solution.
The liquid which results has a green appearence, and may be at once employed for marking linen, since it invariably becomes black after a few days. A steel pen may be employed as well as a quill. If it is desirable not to wait so long for the appearance of the black color, a hot iron may be passed over the writing when the ink is dry, or the linen may be held over the flame of a spirit lamp, or over a hot plate, or hot water, when the black tint will readily appear.
It is a good plan to put the linen when marked into a tepid solution of soap, which has the effect of bringing out a fine blush tint. The ink must be so limpid that it is able to permeate the tissue of the linen, so that the marks appear on both sides.
It is advisable to mix the solutions together, only when the ink has to be made use of.
The ink is perfectly indelible, and so easy to write with that the finest devices may be drawn with it.
A very cheap brown marking ink may be prepared from binoxide of manganese, as follows: 4 pts. Acetate of manganese dissolved in 12 pts. of water.
The place on the linen where the marks have to be made, must be previously moistened with the following solution: 1 pt. Yellow prussiate of potash, ½ pt gum-arabic, 3 pts. water. The linen having been saturated with the above solution, is then dried, and afterwards marked with the manganese solution. On the letters becoming dry, the following solution is spread over the spot with a pencil: 4 pts. Carbonate of potash, 10 pts. water. The letters then become brown, and their color cannot be removed by alkalies, nor by acids, with the exception of dilute hydrochloric acid.
A purple marking ink can be prepared by employing bichloride of platinum: 1 pt. Bichloride of platinum, 16 pts. distilled water.
The place where the letters have to be written, must be moistened with a solution of 3 ots. Carbonate of soda, 3 pts. gum-arabic, 12 pts. water. The spot is then dried and made smooth. After the letters have been written with the platinum ink and become dry, the linen is moistened with a solution of 1 pt. Chloride of tin, 4 pts. distilled water, when an intense and beautiful purple-red color makes it appearance.