(p. 40.) In default of the charcoal-paste, rubbing with the finest emery-paper will do to remove the polish.
(p. 40.) I cannot direct the reader to a copper-planer, and therefore it will be best to give some directions for removing faulty passages. The following paragraphs are copied bodily from Mr. Hamerton:—
“The most rapid way is to use sandpapers of different degrees of coarseness, the coarsest first, and then the scraper, and, finally, willow charcoal with olive oil. The charcoal will leave the surface in a fit state to etch upon.
“This scraping and rubbing hollows out the surface of the copper, and if it hollows it too much the printing will not be quite satisfactory in that part of the plate. In that case you have nothing to do but mark the spot on the back of the plate with a pair of calipers, then lay the plate on its face upon a block of polished steel, and give it two or three blows with a hammer (mind that the hammer is rounded so as not to indent the copper).”
(p. 48.) The process here alluded to is the one used by Mr. Haden. The mordant is the so-called Dutch mordant, and the manner of making it is thus described by Mr. Hamerton:—
“First heat the water by putting the bottle containing it into a pan also containing water, and keep it on the fire till that in the pan boils. Now add the chlorate of potash, and see that every crystal of it is dissolved. Shake the bottle to help the solution. When no more crystals are to be seen, you may add the hydrochloric acid. Make a good quantity of this mordant at once, so as always to have a plentiful supply by you.”
For a full account of the Haden process see Mr. Hamerton's “Etcher's Handbook,” or the second edition of his “Etching and Etchers.”