tympaning

Tympaning is the composite padding material glued to the underside of a letterpress platen, the heavy metal plate that presses paper against inked type. It absorbs impact, distributes pressure evenly across the printed sheet, and protects both the paper and the type from damage during the strike. Without proper tympaning, a letterpress will either fail to print at all or will crush the type and tear delicate stock.

The material itself is typically made from layers of cotton fabric, blotting paper, or synthetic materials bonded together. Traditional tympaning stacks might include a base layer of sturdy cotton sheeting, middle layers of softer packing paper, and a top layer of smooth paper or plastic to accept the impression and wear smoothly. The total thickness is usually between one quarter and one half inch, depending on the platen size and the weight of stock being printed. Different jobs call for different tympaning compositions: brittle papers and large solids need softer padding, while fine detail work and hard papers need firmer support.

When a platen is new, the tympaning is glued or pasted on as a complete sheet. As the press runs, friction and repeated impacts gradually compress and fray the surface. The top sheet will eventually become shiny, glazed, or torn where paper catches on roughened spots. A worn tympan creates uneven impression and marks on printed sheets. Printers strip and replace tympaning as maintenance, a process that requires careful heat application to soften the old glue, scraping away debris, cleaning the metal platen, and pasting on a new sandwich of materials before it is trimmed flush.

The term derives from the Greek tympanon, meaning a stretched membrane or drum. In printing it refers to the entire padded assembly, though the word is sometimes used loosely to mean just the top facing sheet. The distinction matters: tympaning describes the whole stack, while the top sheet alone is often called the tympan or draw sheet. Printers speak of a platen "being out of tympan" when the padding has worn unevenly or hardened from age and no longer accepts impression uniformly.

Tympaning quality directly affects print consistency and waste rates. A hard, glazed tympan produces weak or mottled impression; a lumpy or deteriorating one causes picking and slur. Because replacing tympaning is labour intensive and requires the press to be idle, managing its life is part of press maintenance. Some modern pressmen experiment with synthetic tympaning materials that resist compression longer, though traditional cotton and paper combinations remain the standard in most shops.