Rebiting, if necessary, may be done after rolling up with the resist ink there given, but care must be taken in this rebiting to guard against interfering with the grain of the plate.
CHAPTER III. HALF-TONE INTAGLIOS—(Continued).
The next process under consideration is that in which the grain is given to the copper plate by dusting it with fine powder of resin (colophony) or of asphalt. To do this a dusting box is required, which may be an ordinary aqua-tint box hung on centres for the purpose of revolving it when desired to cover large plates with the powder. The following figure will illustrate a box suitable for small work.
Fig. 15.
The box should be eighteen inches high, twelve inches wide, and eight inches deep; it may be made of cardboard with the inside quite smooth. It should be closed all around except at A, where there is a small door four inches high; the bottom of the box is either studded with small nails or some coarse wire netting is stretched across, upon which the copper plates can rest, as near level as possible. To use this box, four ounces of resin or asphalt are powdered in a mortar until quite fine. The powder is placed inside the box, and the door closed; the box is now vigorously shaken, then placed on the table, the door opened, and a copper plate (previously cleaned and polished) is at once placed face up on the nails or wire netting. By the time the door is opened and the copper plate or plates are in position, the coarser particles of the resin will have subsided, leaving only the fine dust floating in the interior of the box; now close the door, and leave the copper plate within until it is judged that it is powdered sufficiently, which, of course, will be a matter for the operator to find out by practice.
When the plate has been sufficiently powdered, it is carefully withdrawn and placed upon a hot iron plate and allowed to remain there until the resinous {125} powder is just sufficiently melted to adhere to the copper plate, preserving as much as possible the separate existence of each atom of dust. Take care to stop the action of the heat before the resin is melted completely and made to run together and form a smooth surface.
The heat having acted long enough, carefully withdraw the prepared copper from the hot plate and allow it to cool. Any desired quantity of these plates may be prepared and stored away for future use. When they are required the grain may be selected to suit each picture, as the operator can prepare at will (after practice) either a coarse or a fine grained ground.
Instead of using a hot plate the resin may be melted over a gas flame, but the hot plate will be found the best.
There is another method of laying this aquatint ground that is simple and novel, viz., by using the air brush. Those who are in possession of this instrument need no further instructions than to be reminded that ordinary bitumen dissolved in benzole, or a resinous-spirit varnish, is placed in the color reservoir, and then the brush will coat the clean copper plate with an aquatint as fine or as coarse as required, according to the distance between the plate and the “brush.” Another advantage with this method of laying the ground is, the ground need not be even, as in the dusting method, but the artist may lay the ground coarse in some places and fine in others, verb sap.