ROUND ETCHING.
Its object is to remove the last formed grade. Coat the plate with a very uniform coating of ink, corresponding to the one used in middle etching. A {91} criterion for correct coating is, that only the grade caused by middle etching be covered, while the grade from deep etching must remain exposed. Remember also that in heating the plate a further spreading is caused by melting.
To the inexperienced it may happen that the grade caused by deep etching is of variable width. These places must be removed by working over with a graver before continuing, as otherwise we will not attain symmetrical round etching.
The plate prepared for the latter treatment is only dusted once in resin, and then blown out. It is then heated to 45° C., and is dusted and heated twice with asphaltum at increasing temperature, just as in both the previous processes. Nothing now remains to be scratched away. After having varnished the back, the plate is etched in the middle etching bath two or three times for three minutes. At the end of each period examine whether another whole period is necessary, or whether rounding the plate requires less time. When this is over (several parts, which perhaps were already finished beforehand, have been covered), wash and approach the next problem, the removal of the grade resulting from the middle etching. This is called
CLEAN ETCHING.
Upon the clean, smooth rollers spread thick transfer ink and roll it out perfectly. It is advisable to warm the stone previously with a little alcohol, which promotes the working out of the color. When the surface of the color has become perfectly uniform the plate is rolled in slowly and without pressure. Pressure would deposit too much color in the finest recesses, and prevent the clean etching and sharpening of the same, thus causing lack of harmony in the prints.
It is better to coat the shadows with a pad, as they require more color.
The plate, thus blackened, is to be dusted once with the finest asphalt powder, then freed from excess by dusting off and blowing until the coating becomes brilliant.
Clean etching then takes place in the bath for etching on, in periods of one minute each, and repeatedly until the last thread has disappeared.
Now everything is ready for a proof, and for subsequent mounting.