To sum up:—
Charcoal and scraper are used to remove part of the surface of the copper. The furrows, having been reduced in depth, receive less ink in printing; the lines gain in delicacy in the impressions.
The burnisher simply displaces the copper; charcoal and scraper wear it away. It follows that they must be used with discernment.
54. Hammering Out (Repoussage).—These three means are employed when a moderate lowering of the plate is required. When it becomes necessary to go down to half the thickness of the plate or more, the result will be a hollow, which will show as a spot in printing. In that case recourse is had to the fourth means; that is to say, to hammer and anvil. Get a pair of compasses with curved legs (calipers); let one of the legs rest on the spot to be hammered out; the other leg will then indicate the place on the back of the plate which must be struck with the hammer on the anvil. In this way places which have been reduced with charcoal or scraper may be brought up to the level of the plate; but if the lines should be found to have been flattened, which would result in a dull tone in the proofs, it will be best to have the part in question planed out entirely, and to do it over.
55. Finishing the Surface of the Plate.—The charcoal occasionally leaves traces on the plate, which show in the proof as rather too strong a tint. You can get rid of them, by rubbing with a piece of very soft linen, and the paste obtained by grinding charcoal with oil on a fine stone.
By the same process the whole plate is tidied. It is likely to need it, as it has undoubtedly lost some of its freshness, owing to the abuse to which it was subjected in passing through all these processes.
Our young pupil, having executed these several operations, and bitten his retouched plate, submits a proof to my inspection, which I compare with that of the first state (Pls. Ia and I.). Now you see, I say to him, how one state leads to another. You have come up to the harmony of the original; your second state is satisfactory, and so there is no need of having recourse to varnishing the plate a third time.
Pl. I.
