impose

To impose is to arrange columns of type or printing plates into the correct sequence and position on a press bed, then lock them into a metal frame called a chase using wedges and furniture. This preparation step transforms loose components into a locked-down form ready for the printing run. On a flatbed press, the composed pages or plates sit on a steel surface called an imposing stone while the worker positions each element according to a layout diagram, then applies pressure through quoins (expandable metal wedges) to hold everything rigid.

The term comes from the Latin imponere, meaning to place upon, which describes the literal action of setting type onto the stone or bed. In hand letterpress work, the imposition diagram shows page numbers in their printed sequence, not reading order, so that when sheets are folded after printing, pages fall into correct order. A 16-page signature, for instance, requires pages 1, 2, 15, 16 to sit adjacent on the press bed so that after folding and trimming they form consecutive pages in the bound book.

Imposition variants and presswork

On cylinder and rotary presses, the imposition process differs because curved stereotype plates or flexible photopolymer plates wrap around cylinders rather than lying flat. The platemaker must account for circumference and wrap tension when positioning elements. Work-and-turn imposition prints one side of a sheet with all pages correctly positioned, then the sheet is flipped and reinserted to print the reverse side using the same chase and plates. This economical method reduces setup time on small-format jobs but demands precise positioning and feeding discipline.

Poor imposition causes printing defects: pages out of sequence after folding, gutters too tight or too wide, marginal text cut off during trimming, and misalignment between front and back. Quoins that slip during the run or wooden furniture that absorbs moisture and swells can shift the locked form microscopically, visible as creeping or slurring on impressions. Modern imposition is now handled by prepress software that generates film or plates correctly positioned from the start, but the term persists in general printing vocabulary and remains essential in hand-set and small letterpress shops.