PACKING

A normal platen press packing is about .035–.040 inches. A supply of precut packing and draw sheets in .002 and .003 thicknesses and oiled manila tympans of .006 inch is handy. The tympan and one or two draw sheets should be clamped together under the bottom bail. The corners of the tympan may be clipped off to help pull it tight and smooth against the platen. The purpose of the draw sheets is to provide a substrate held in register with the tympan, not loose and free to slide around. The thicker lip of the sheets together also makes the bottom bail clamp more firmly. Only the tympan need be held by the top bail; when opening the packing, the bottom bail remains in place.

The rest of the packing can be composed of miscellaneous materials. There is room for considerable experiment here. Mylar, latex dental dam, cloth, tag, blotter paper, pressboard, newsprint, carbonless paper may be useful at one time or another. In general, pressboard of .030 inch leaves scant room for modifications. My own preference is for packing paper, tag, and .005 or .007 mylar.

In general, if impression is too heavy at the bottom of the form, packing should be removed; if too heavy at the top of the form, packing should be added. Examine the back of the sheet against a raking light. Chandler and Price Craftsman presses have a wheel behind the press by which the angle at which the bed meets the platen can be adjusted. Likewise, Heidelberg platens allow the impression to be changed with the impression lever. Both arrangements simplify the process of making the impression at once even over the whole form, and of correct strength. On presses which allow impression to be changed only by adding or taking away packing, it is possible to adjust the the height and angle of the platen by means of screws under the platen, but such adjustment is not easy. It is an adjustment one would like to make once and be done with. If, over time, it seems that the press is consistently weaker or stronger on one side or corner, the screws under the platen should be adjusted. The screws in the corners are held by nuts which must be backed off before the screws are turned. Turn the screws only slightly: often just a sixth turn will raise or lower the platen enough. The central screw is intended only to support the center of the platen. It should be backed off, the platen adjusted by the other screws, and then snugged up again. Retighten the locknuts when done.

Heavy Impression

There is at present a vogue for deep impression. Although without historical basis, it is likely to persist, since the customer can see no other reason to spend the additional money for letterpress printing. (And letterpress must cost more than offset, must it not, else offset would not have supplanted letterpress. If you find you are repeatedly winning bids to produce by letterpress work which could be done by offset, charge more.) Many designers have come to believe that impression is an independent aesthetic variable properly under their control. In fact, impression is part of a constellation of interdependent technical variables, including packing, roller setting and ductility, and ink tack and coverage, all properly under the control of the pressman. On any given job, correct impression implies a narrow range, in which the resistance of the paper surface to the impress of the printing elements is just sufficiently overcome to render their designs faithfully.

The good side of the demand for heavy impression is that makeready is simplified; finesse is seldom required, and the customer is easily pleased. Letterpress finds a niche it can fill profitably. The main problem for the printer is to keep the type from printing on its neck as well as its face. Hard rollers, a light setting, tacky ink, light coverage and double-rolling, and frequently brushing out the form with typewash may help. A hard packing seems to allow a deep impression on the printed side of the sheet without unduly punching through the back of the sheet; a soft packing promotes the look of deep impression. Customers often judge this printing by their fingers, not their eyes.

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