preboard

Preboarding is a heat-setting operation in hosiery and knitwear production where a wet or damp knitted garment, typically a stocking or sock, is stretched onto a heated metal form and held there until dry. The form, essentially a mould shaped like a leg or foot, locks in the intended dimensions and straightens any creases or distortions from the knitting and initial handling stages.

The process is performed before dyeing because the garment must be stable and true to specification when it enters the dye bath. Heat from the form (usually 80 to 120 degrees Celsius) fixes the knit structure temporarily; the fibre, whether nylon, cotton, or wool, sets into that shape. Without preboarding, subsequent wet processing would cause the garment to shrink unevenly or distort, and any size variation would be amplified by the dye house. The result is a stocking that emerges from dyeing with consistent leg length, foot length, and girth.

Modern preboard units are often semi-automated, using gas or electric heating with forms that are loaded horizontally or vertically. The garment sits on the heated form for 15 to 45 minutes depending on fibre content and wall thickness. Some machines use infra-red heaters or hot air circulation to speed drying; others rely on radiant heat from the form itself. After cooling, the garment is removed and typically allowed a brief air rest before dyeing.

Preboarding also serves a secondary role: it identifies and removes visibly defective pieces before they consume dye and labour. A twisted leg, a dropped stitch that has run, or a hole becomes obvious when stretched on the form and is culled at that point rather than discovered downstream.

The term reflects the simple origin of the technique: early textile workers used flat heated boards or shaped wooden forms to set hosiery by hand. The vocabulary has remained unchanged even though the equipment is now mechanical. Preboarding is standard in any hosiery mill that produces dyed goods; it is less common or unnecessary in piece-dyed continuous processes where the knit structure is locked by the dye chemistry itself, though even those operations often include a light heat-set step for dimensional stability.