block

In letterpress and relief printing, a block is a substantial piece of hardwood, usually maple or end-grain boxwood, that serves as the structural backing for a stereotype or electrotype printing plate. The plate itself, whether cast lead alloy or electroformed copper, is mounted flush on the block's upper surface and secured with lead or solder. The block's dimensions match the press chase and its thickness, standardized at 0.918 inches (a legacy measurement called "type height"), allows the assembled plate to print alongside movable type without makeready adjustments.

The choice of wood matters considerably. Maple provides stability and resistance to the moisture fluctuations of the pressroom; boxwood, denser and tighter-grained, permits finer detail work during mounting but is more expensive and less commonly used for production work. The block must be perfectly flat and free of warping, as any deviation will cause uneven pressure and spotty printing. Softwoods are avoided because they compress under the tonnage of a printing press and fail to hold plates securely over thousands of impressions.

Mounting a plate to its block involves careful centering and mechanical fastening. Lead slugs or solder applied around the plate perimeter lock it in place; some printers drove small brass nails through the wood into the plate's underside. The underside of the block is often beveled or routed to reduce weight and material cost while maintaining rigidity. Old blocks sometimes bear mounting traces from multiple plates, evidence of their long service life.

The term "block" has largely disappeared from active printing vocabulary as letterpress declined through the twentieth century, overtaken first by photogravure and lithography, then by offset and digital processes. A modern offset pressman would not recognize the word in this context. However, the block persists in hand printing, fine art printing, and relief printmaking studios where traditional methods endure. Printers and collectors of antique printing equipment still specify blocks by their original dimensions and their fitness for particular plate formats.