Photo-engraving, Photo-etching and Photo-lithography in Line and Half-tone / Also Collotype and Heliotype

by W. T. Wilkinson

CHAPTER II. INK PHOTOS.

The various methods named in the last chapter for breaking up and transferring to stone the delicate half tints of a photograph from nature, are in a great measure rather crude and do not give the fine results yielded by the following modification of the collotype process, nor are they so certain and simple in their working.

The production of ink photos is as follows: A plate of flat copper is grained by means of graining sand and a piece of litho. stone, the sand being put through a fine sieve (about 120 holes to the inch). The copper plate being, first of all, well polished and without scratches, is placed upon a flat board, the graining sand is then sieved over it, and moistened, then with a light, firm motion of the wrist, the whole of the surface is evenly ground. The operation of graining is very difficult to describe, except to say that the stone muller is shuffled all over the plate until the polished surface of the copper is replaced by an even matt. Renew the sand when necessary. Do not try to get through the operation rapidly by taking large circles, else scratches are sure to result.

The copper plate being grained, it is well washed, back and front, so as to free it from all grit, then coated whilst wet with

Stale Beer (not lager)	5	ounces.
Water	5	ounces.
Silicate of Soda (syrupy)	1	ounce.
Tannin	1	grain.

Shake well, then filter; coat the plate twice and stand it on a rack to drain and dry. When dry swill the plate under the tap and again dry. These plates may be prepared in advance, as they improve by keeping.

Now prepare the following solutions:

	Best Cologne Glue	1	ounce.
	Water	10	ounces.
When dissolved add
	Bichromate of Potash, in powder	30	grains.
Stir until dissolved, then add
	Nitrate of Silver	30	grains.
	Dissolved in Water	1	ounce.
Stir well, then add
	Chloride of Calcium (crystals)	10	grains.
	Dissolved in Water	1	ounce.
Stir up well, then add
	Acetic Acid	1⁄2	drachm.
Again stir.

Warm the coated copper plates by letting them lie upon the slab of the drying oven. The drying oven is described in the chapter on collotype printing, and for this process the slab should be at about a temperature of 150° F. Now strain the above mixture through muslin into an invalid’s cup with a long spout, and holding the warm copper plate horizontally on the palm of the left hand, proceed to pour over it as much of the gelatine mixture as will well cover it. Do not have a very thick film, else the grain will be too coarse; nor too thin, or there will be no grain at all. Practice will soon enable the operator to apportion the proper quantity to each plate. As a rough estimate, about one fluidounce of the mixture for a plate 12 × 10 will be required.

The plate being coated, it is placed on the slab of the drying oven and left there until dry. That will take from one and a half to two hours. The exact temperature at which to dry these films cannot be arbitrarily stated, as so much will depend upon the picture which is to be printed; therefore, a few experiments will be necessary before settling down to an exact form of working. A good plan that answers admirably is to raise the water in the tank of the drying oven to boiling point before coating the plate, then coat the plate, lay it on the slab, let the water in the tank boil for a few minutes then turn out the gas and let the plate dry.