monoline

A monoline is a keyboard-operated typecasting machine that casts an entire line of type as a single metal block, or slug. The operator taps keys corresponding to letter matrices; these matrices drop into a line, which is then justified to the correct width, surrounded by brass spacing material, and rolled under a plunger into molten type metal. The result is a solid metal bar, typically lead alloy, bearing the complete line of characters in relief on its upper edge. This slug ejects into a galley and is ready for immediate use in the printing forme.

The Linotype machine, invented by Ottmar Mergenthaler in 1886, is the dominant monoline design. A competing system, the Typograph, operated on similar principles but found limited commercial success. Both machines required a trained operator and demanded regular maintenance of casting equipment, circulating hot metal pumps, and the brass matrix mechanism. Justification was mechanical, achieved by wedge-shaped spacebands that were forced apart between words until the line reached set width.

Advantages and limitations

The monoline machine's great advantage was speed: a skilled operator could compose around 6,000 characters per hour, dramatically faster than hand composition. The slug format simplified lockup in the printing forme and reduced pi (scattered type) since entire lines could be removed as units. Type never needed sorting after use; slugs were simply melted down and recast. However, monolines could not handle tabular matter, equations, or complex layouts without hand-set type supplementing them.

Quality issues included uneven letter spacing on tight lines, where justification might force matrices too far apart, and casting flaws if metal temperature or pump pressure fluctuated. Corrections required removing the entire line and recasting it. The machines were substantial, noisy, and required operators with both dexterity and knowledge of typographic conventions, word breaks, and line length calculations.

Monolines dominated newspaper and book composition from the 1890s through the 1960s. They declined sharply after phototypesetting systems emerged in the 1950s and 1960s, which offered faster output and greater flexibility. By the 1980s, the machines were obsolete in professional printing, though some hobbyists and specialty letterpress printers continue to maintain and operate them.