These are intended for use with rubber stamps, (a) The ordinary stamping-ink made by diluting printing-ink (which is made of lampblack and linseed varnish) with boiled linseed oil, stands pretty well if enough is used, but when poorly stamped will wash off. Dr. W. Reissig, of Munich, has recently made an ink for cancelling stamps which is totally indelible, and the least trace of it can be detected chemically. It consists of 16 parts of boiled linseed-oil varnish, 6 parts of the finest lampblack, and 2 to 5 parts of iron perchloride. Diluted with \ the quantity of boiled oil varnish, it can be used for a stamp. Of course it can only be used with rubber stamps, for metallic type would be destroyed by the chlorine in the ink. To avoid this, the perchloride of iron may be dissolved in absolute alcohol, and enough pulverized metallic iron added to reduce it to the protochloride, which is rapidly dried and added to the ink. Instead of the chloride, other salts of protoxide or peroxide of iron can be used. The iron unites with the cellulose and the sizing of the paper, so that it can easily be detected even after the ink has all been washed off.
Sulphide of ammonia is well adapted for its detection. (6) A violet ink for rubber stamps is made by mixing and dissolving 2 to 4 dr. aniline violet, 15 oz. alcohol, 15 oz. glycerine. The solution is poured on the cushion and rubbed in with a brush, (c) The following is said to be a good ink for use with rubber stamps: - Aniline violet, 90 gr.; boiling rain-water, 1 oz.; to which is added a little glycerine and a small quantity of treacle. The quantities of the last two ingredients will vary with the season, but half a teaspoonful will be ample for the quantities of violet and water specified, (d) Red. - Dissolve 1/4 oz. of carmine in 2 oz. of strong water of ammonia, and add 1 dr. of glycerine and 3/4oz. of dextrine , (e) Blue. - Rub 1 oz. of Prussian blue with enough water to make a perfectly smooth paste; then add 1 oz. of dextrine, incorporate it well, and finally add sufficient water to bring it to the proper consistence. (f) For linen and cotton. - Dissolve 1 part of asphaltum in 4 parts of oil of turpentine, and add lampblack, or blacklead, in fine powder, in sufficient quantity to render the ink of a proper consistence for printing with types. (g) The cushions or pads generally used in connection with rubber stamps require fresh supplies of ink from time to time; but lately a cushion has been devised which will give off colour "permanently," i.e. until it is all used.
This consists of a box of wood, or other material, filled with an elastic composition saturated with a suitable colour. The cushion fulfils its purpose for years without the material being renewed, always contains sufficient moisture, which is drawn from the atmosphere, and continues to act as a colour stamp cushion so long as a remnant of the mass or composition remains in the box or receptacle. The composition consists preferably of 1 part gelatine, 1 part water, 6 parts glycerine, and 6 parts colouring matter. The composition can also be made from a mixture of gum with borax, ordinary Chinese glue, and other similar materials. A suitable black colour for the cushion can be made from the following materials: 1 part gelatine glue, 3 parts of lampblack, aniline black, or a suitable quantity of logwood extract, 10 parts glycerine, 1 part absolute alcohol, 2 parts water, 1 part Venetian soap, | part salicylic acid. For red, blue, or violet - 1 part gelatine glue, 2 parts aniline of desired colour, 1 part absolute alcohol, 10 parts glycerine, 1 part Venetian soap, and 1/5 part salicylic acid. For blue - also indigo, ultramarine, cobalt, Prussian or Paris blue.
For red - vermilion or carmine; and for green - aniline or other suitable colouring matter.