Every maker of zinc and aluminium plates supplies this special etching solution, prepared for a certain quality and character of metal. It is advisable, therefore, to use the preparation recommended, and thus avoid the many pitfalls which beset the path of the experimentalist.
“The plate is now well washed over with clean water, and thinly gummed up. When the gum is dry wash out the work on the top of the gum with dry flannel or felt till all the work is removed, sprinkle a few drops of water on the plate, and with a rubbing-up rag and a little ink and turps rub up the work till it is gently charged with ink, then roll up till work or transfer looks strong and sharp, when the plate is ready for printing.”
For etching and rolling up chalk drawings on grained plates: “Pour in a saucer some of the etching solution, and add about the same quantity of fresh, strong gum. This solution is evenly distributed all over the plate with a camel-hair brush, and left to dry. Then the etching is removed with water, and the plate very thinly gummed up and left to dry. Now the work is washed out with turps and a piece of dry, soft felt or flannel, without water, till all the work disappears, and the plate rolled up solid black. Then sponge over with water-sponge, damp over and roll up till work appears nice and sharp. Now dust over with resin and French chalk, and etch again with the etching solution, full strength. After the etching has dried remove the same with water, and gum up again.
“When drawings are to be washed out for proofing or printing, the plate should first be thinly gummed up. This gum layer is left to dry thoroughly, and is not removed when the work is washed out (without water) with turps and a dry piece of flannel or felt. Next wipe away all the black ink and turps, still using no water for this operation. Should any black work be left, use some more turps on the clean dry rag till all the work has been removed, then sprinkle a few drops of water on the plate, and use a clean rag to remove the gum layer and loose black ink left on the plate, then damp over as usual and roll up.
“Plates treated in this way retain the grease contained in the drawing, and the work rolls up easier and quicker, and none of the finer work gets weakened or lost; also, the plate keeps cleaner and free from scum.
“When alterations are necessary the work should be rolled up with a strong black ink, and dusted over with French chalk (powdered talc). Remove the part which requires altering with a mixture of equal parts etching solution and turpentine on a small piece of felt or flannel, and rinse well with water. Pour some special re-preparing solution in a saucer, and apply this solution with a camel-hair brush to the parts where the work has been removed; after the solution has remained for a few seconds rinse well with water. This operation is to be repeated several times till the surface looks clean, no work being visible; and after the plate is dried with clean white blotting paper it is ready to receive the additional work. When the alteration has been made, the rolling up should be done with the bichromate solution, as per general directions.
Fig. 22.