To produce the desired effect, great nicety and patience are required in the pressman: a single thickness of thin India paper, (the best for overlaying,) with the edges scraped down, is frequently required over very small parts. The overlay should never be cut at the edges; but, even where great delicacy of shape is not required, it should be torn into the form wanted: this reduces the thickness of the edges, and causes the additional pressure to blend with the surrounding parts As particular parts of the impression will frequently come up too strong, and other parts too weak, it will be necessary to take out from between the tympans a thickness of paper and add an additional tympan-sheet, cutting away the parts that come off too hard, and scraping down the edges. Scraping away half the thickness of a tympan-sheet in small parts that require to be a little lightened will improve the impression. The light parts require little pressure; but the depths should be brought up so as to produce a full and firm impression. If a block be hollow on the surface, underlaying the hollow part will bring up the impression better than overlaying it, at least so nearly that only a thickness or two of paper will be needed as overlays. If a block be too low, it is better to raise it to the proper height by underlays than to use overlays; as the latter act in some measure as blankets, and are pressed into the interstices, rendering the lines thicker than in the engraving. It will be necessary sometimes, when the surface of the block is very uneven, to tear away parts of the paper in the tympan, to equalize the impression where it is too hard. The pressman will find it convenient to pull a few impressions, while he is making ready, on soiled or damaged India paper. Out of these he can cut overlays to the precise shape and size wanted, which are always necessary when great accuracy is required in overlaying particular portions. He should be provided with a sharp penknife and a pair of good small scissors. A fine sharp bodkin and a needle or two, to take out picks, are also needful; but he should be particularly careful so to use them that he do no injury. The best way is, to draw the bodkin or needle point cautiously in the direction of the lines.