To sharpen an etching-needle, pass it over the oil-stone, holding it down flat, and turning it continually. When it has attained a high degree of sharpness, describe a large circle with it on a piece of card-board, holding it fixed between the fingers this time, and go on describing circles of a continually decreasing size. The nearer you approach to the centre, the more vertical must be the position of the needle. The fineness or the coarseness of the point is regulated by keeping the needle away from, or bringing it nearer to, the central point.
The dry point must be ground with flat faces rather than round, so as to cut the copper, and penetrate it with ease.
If the burnisher is not sufficiently polished, it scratches the copper, and produces black spots in the proofs. To keep it in good condition, cut two grooves, the size of the burnisher, in a piece of pine board. Rub it up and down the first of these grooves, containing emery powder; and then, to give it its final lustre, repeat the same process, with tripoli and oil, in the second groove.
The stones which are too hard for razors are excellent for the scrapers. Having sharpened the scraper with a little oil, during which operation you must hold it down flat on the stone, pass it over your finger-nail. If the touch discloses the presence of the least bit of tooth, and if the tool does not glide along with the greatest ease, the grinding must be continued, as otherwise the scraper will scratch the copper.
You are at liberty to use two troughs,—one for the acid bath; the other, filled with water, for washing the plate.
A glass funnel, and a bottle with a ground-glass stopper, will be necessary for filling in and keeping the etching liquid.
Various substances are used for finishing off the copper plates; the most natural is the paste obtained by rubbing charcoal on the oil-stone with oil.
Then comes the fine emery paper Nos. 00 or 000, rotten-stone, tripoli, English red, and, finally, slate. Powdered slate, produced by simply scraping with a knife, is excellent, used with oil and a fine rag, the same as other substances.
The varnish for revarnishing is nothing but ordinary etching-ground, dissolved in oil of lavender. It must be about as stiff as honey in winter.
The rollers for revarnishing, which can be had of different sizes, are cylindrical in form, and are terminated by two handles, which revolve in the hands. The roller ought, if possible, to cover the whole surface of the copper.[5] As soon as it has been used, it must be put out of the way of the dust.