fall out
To fall off due to the quoins holding it in place having become wet and therefore loose.
fall out: type loosens when quoins absorb moisture
In letterpress printing, fall out describes the unwanted ejection of metal type or other matter from the forme (the assembled block of type locked into the chase) during a print run. The type literally falls away from its position, disrupting the print and often scattering sorts across the press bed or floor.
The mechanical cause was moisture ingress into the quoins, the wooden or metal wedges used to lock type tightly into the chase. Wood quoins, common in hand presses and early steam presses, swell when exposed to dampness from cleaning water, steam, or humid workshop air. As they expand, the pressure they exert on the forme decreases, allowing type to shift and separate. Metal quoins (steel or cast iron) could rust or corrode at their bearing surfaces, reducing grip. Either way, the type became loose enough to dislodge under the mechanical shock of the platen striking the forme.
Fall out was most hazardous on high-speed cylinder and platen presses where impact forces were greatest. A single piece of type departing the forme could strike the operator, damage the impression surface, or leave a void that printed as white space. Repetitive fall out on a run indicated either poor quoin maintenance, inadequate forme pressure, or unsuitable ambient conditions in the pressroom.
Prevention and the shift to modern locking
Printers managed the risk through careful quoin storage in dry conditions, regular inspection of quoin surfaces and threads, and adjustment of pressure before high-speed runs. The adoption of mechanical and pneumatic quoin systems in the mid-20th century, along with purpose-built locking bars, made fall out obsolete. Modern presses use hydraulic or screw-based locking that does not depend on material swelling or corrosion.
The term has largely vanished from active printing vocabulary as metal type itself became less common after phototypesetting arrived in the 1960s and 1970s. Archives and hobby letterpress shops still understand the phrase, but it now describes a historical failure mode rather than an operational concern.