In making ready, it must be evident that, when a clear, sharp impression is wanted, the pressure should be on the surface only. Of course the tympan ought not to be very soft, neither should a woollen blanket be used: the most perfect impression will be obtained when fine thick paper alone is placed in the tympans; and even of this article but few thicknesses should be employed. After an impression is printed, the pressman examines if it be uniform throughout; if it be,—which is very rarely the case,—he goes on with the work; if not, he proceeds to overlay, in order to produce regularity of pressure and of colour over the whole form. Wherever the impression is weak he pastes a bit of thin, smooth paper, of the size and shape of the imperfect part, on the tympan-sheet; he then pulls another impression, to examine the effect of his overlays, and continues to add to them where wanted, till the pressure of the platen is the same in every part and the impression is of a uniform shade of colour. If the impression come off too strong in parts, or at the edges or corners of the pages or on the head-lines, it will be necessary to cut away the tympan-sheet in those parts, and, if that does not ease the pressure sufficiently, to cut away the same parts from one or more of the sheets that are within the tympans. It is generally preferable to overlay on a sheet of stout smooth paper inside the tympan, particularly where the same press does the whole or great part of the work: this sheet is cut to fit the interior of the tympan, so as not to slip about, and has overlays pasted on it where wanted, to bring up the impression till it is very nearly equal. In all succeeding sheets it saves the pressman a great deal of time, as he will be certain that when he pulls a sheet of another form of the same work it will be nearly right, and he will only have to place thin overlays on occasional parts to make the impression perfect. It is necessary, where short pages occur in a form, to have bearers to protect their bottom lines and the edges of the adjoining pages. These may be of double pica reglet, pasted on the frisket, so as to bear on some part of the furniture or chase; but bearers made to the height of the types are better, when they can be used. It happens occasionally that the tympan causes the paper to touch the form partially on being turned down, and occasions slurs. This may occur from the parchment being slack or the paper being thin and soft. To prevent this inconvenience, it is customary to roll up a piece of thick paper and paste it on the frisket adjoining the part. Many pressmen prefer pieces of cork cut to about the thickness of double pica, and pasted on the frisket.