The best printing frames for collotype printing are of the box (or “deep”) pattern, with plate glass fronts. They should be about two inches deep, and the bars behind quite plain—i. e., without either screws or springs. The back board should also be dispensed with, the pressure being got by means of wedges. The advantage of these frames is that the picture can be examined without undoing the back, and without risk of shifting the plates.
After printing, the plate should be placed in a zinc vessel like a plate box fitted with a siphon, so that the water can be kept constantly changed, until the bichromate is removed; then the plate is drained, and, after being wiped with a soft cloth, is put away to dry.
Now then, beginners, do not be in a hurry to try your first plate on the press directly it is free from the bichromate, as no plate will give a good result until it has been dried down. Before putting it on the press, soak it for half an hour in water, then half an hour in glycerine and water in equal parts, and, finally, wipe it, and proceed to ink up the press.
The safest plan is the one mentioned, viz., bedding up slate with plaster-of-Paris. Another plan is to place on the iron bed of the press a piece of thin felt, then a slab of glass, upon which are placed two thicknesses of wet blotting-paper; upon these place the collotype plate (the back of which is free from any gelatine that may have run over after coating); then, if a chase be placed on the press, the plate may be blocked in position by means of a few pieces of furniture tightened by means of quoins.
In the above only glass slabs are treated of; but brass plates, about one-eighth of an inch thick, will be found safer, and more economical than glass, and yield results just as good. They may be fixed upon a block of hard wood by means of a screw (countersunk) at each corner. If an ordinary type press is not at hand, brass plates may be printed from upon a litho. press.
Whether the plate will require damping each time will depend greatly upon each individual plate and the subject. With some, damping must be done each time; with others, once only for four, six, up to a dozen pulls; but, of course, the temperature of the room in which the printing is conducted will be an important factor in determining this point. When the print is flat, and the whites degraded, then damp the plate before again inking up. {177}
To insure even prints, care must be taken to keep the roller well charged with ink. Much more could be written on this subject, but practice will be the best guide.
A word as to bedding the glass slab on. With a properly prepared leather litho. roller, charged with ink mixed with a little olive oil and varnish, brought to a working consistency with a muller on a smooth slab (be sure that the ink on the roller is evenly distributed), after wiping the plate carefully with a soft, damp cloth, proceed to ink up the image slowly and carefully; then, when all the ink possible has adhered to the image, take the glue roller and apply it three or four times, which will clear the image wonderfully. Now put the mask in position—either a cut-out, or four narrow strips of bank-post coated with gold size and oil, and then dried—then put a piece of mat enamel paper in position, then a piece of common printing paper on top, then a piece of blanket; lower the tympan, run in the bed, and press, and, if the pressure is not too much, the prints will be just as good; but, if too much pressure be used, the paper will be creased and spoiled, and the collotype image is in danger of being cut.
CHAPTER V. THE NEW HOME PRINTING PROCESS.
There is a method of making reproductions from photographs without any photographing process further than that required to supply the print. Any good photograph with a matt surface may be traced over with the ink supplied for the purpose by the inventor of the process, or with the ordinary lithographic autographic ink, which comes in sticks like India-ink, and then the superfluous portions faded away (or not) as directed on a preceding page. From that or from a crayon sketch, music, a written letter, plans, or circulars, in fact, from anything written with the proper ink with a pen or printed, reproductions may be made. The principal appliances needed are the “Universal Copying Machine” and its accessories.