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

by W. T. Wilkinson

Now place the pewter on the bed of the press, and with a clean sponge cover the picture with clean, cold water, in sufficient quantity to form a pool about one-eighth of an inch deep, care being taken that the water does not extend as far as the edges of the skin.

The water is allowed to remain on the skin for five minutes; it is then soaked up, and a fresh supply added, and this operation is repeated at intervals for twenty or thirty minutes, the object being to partly remove the bichromate, and also to allow the gelatine that has not been rendered insoluble by the action of light, to absorb sufficient water to enable it to repel the ink from the roller.

When it is judged that the image has been sufficiently soaked, with the sponge remove as much water as possible, then lay a clean sheet of paper upon the skin; upon the paper lay the loose blanket, lower the tympan, run the bed of the press under the platen, then pull over the lever, and subject to as much pressure as the press will give, allowing the pressure to “dwell” for a minute or two.

This is to “smash” down the highest relief in the skin, which, unless so smashed down, would interfere with the roller feeding the ink in the deepest shadows.

The skin is now ready for inking up with No. 1 roller, charged with the best litho. ink mixed with a little lard, just sufficient, and no more, to make the stiff ink distribute on the slab, the ink and the lard being thoroughly incorporated, either with a stiff palette knife or with a muller. The ink and lard being thus well mixed upon the slab, gather up the compound and place it in one corner of the slab.

For No. 2 roller take a portion of the above mixture and add to it a little more lard, and mix well, then place this in one corner of the other inking slab.

With the palette knife touch the roller No. 1 at short intervals with little dabs of the first ink, then roll it vigorously on the slab up and down, and then {161} across and sideways, until the ink is evenly distributed over the roller and the slab; now with the roller proceed to ink up the image. Use plenty of pressure, and turn the roller first one way, then the other, until the image shows itself vigorous and strong.

Now take No. 2 roller charged (in the same way as No. 1) with No. 2 ink well distributed (but do not use quite so much as with No. 1), and with a light pressure go over the inked image; this inking will fill up the light half-tones and clean up the image generally.

Before pulling an impression take a sheet of mask paper (which must be a little larger than the pewter plate), and in the centre cut a clean, sharp opening the size the picture must be. This mask, with the oiled side down, is adjusted in position on the skin; then turn back the edge furthest from the operator, and upon the extreme edge of the pewter place a few small dabs of stiff ink, return the margin of the mask over these dabs of ink, and rub down; these dabs of ink serve to keep the mask in position, when turned back for each inking up. If the margin of the mask paper projects over the pewter plate, and outside the bed of the press, it must be turned down, else it will tear when the bed of the press is run in.

The mask being laid in position to protect the margin of the print, lay a piece of matt enamel paper on the inked up and masked image, back this first with a sheet or two of clean blotting paper, then with a loose blanket; lower the tympan, and run the bed of the press under the platen and pull over the lever. The pressure requisite to pull an impression from a heliotype skin requires the full strength of an ordinary man to pull over the lever.