Letterpress printing

Letterpress printing refers to the process of relief printing using hard plastic or sometimes metal printing plates. While flexo printing uses rather liquid dyes that may be metered by engraved rolls (anilox), letterpress inks are heavy pastes similar to inks used in lithography and must be metered by a complicated series of rollers.

Letterpress printing is not usual on packaging; it is mostly used for printing stickers and labels. Letterpress printing plate is more robust, but its production is much more expensive than the usual flexo printing plate. Inflexible plates are more stable in terms of their dimensions than flexible polymer plates (for flexo printing) and a finer colour matrix may be used, resulting in better quality prints.

Cylindrical objects such as two-piece metal cans have no circumferential register point but only position register. The problem is resolved by a process modification variously known as offset letterpress, dry offset or letterset.