typeform

A typeform is the complete assembly of metal type, spacing material, and furniture locked into a rigid rectangular frame called a chase. It sits on the bed of a printing press and receives the full force of the platen or impression cylinder during each printing stroke. The typeform must be perfectly level and immobile, or the printed impression will be uneven across the sheet.

The type itself, typically cast from a lead alloy, sits face-up in the chase. Metal spacing blocks and leads (pronounced ledds) fill gaps between lines of type; wood or metal furniture surrounds the outer edges. All pieces are locked tight using a system of quoins, wooden or metal wedges that expand against the chase walls when tightened with a specialized key. A loose typeform will slip during printing and ruin the job.

Building and locking a typeform

The printer assembles the typeform on a composing stone or galley, checking alignment with a typescale and straightedge before locking. The locked form must resist lateral movement under impression pressure, which can reach several tons per square inch on a platen press. Printers use a traditional plumb to verify that the type face is truly perpendicular to the chase bed, since even slight tilting causes one edge of each character to print darker than the other.

Different press types require different typeform preparations. A flatbed cylinder press can hold larger typeforms than a platen press; a rotary press requires type to be stereotyped or electrotyped onto a curved shell rather than locked flat. The term typeform is specific to relief printing (letterpress). In offset lithography, the image exists on a metal plate, not as assembled type.

Typeforms became less common as offset printing displaced letterpress from the 1950s onward, but specialty printers and hobbyists still lock type daily. The skill lies in understanding how metal, wood, and wedges behave under pressure, and why a typeform that looks tight on the stone may shift once the heavy impression begins.