Compacting

A knit comes off the circular knitting machine with its loops stretched wider than they want to sit at rest, and washing later lets them relax back — that relaxation is shrinkage. A compactor, usually a heated roller and felt-belt setup running the greige goods through under controlled tension, physically pushes the loops closer together before the fabric is ever cut into pattern pieces. Done well, it takes a fabric that would lose 8-10% of its dimensions in the customer's washer down to something in the 3-5% range.

This is the quiet reason two tees at the same 5.3 oz weight behave so differently after a wash. Bella+Canvas runs its Airlume combed cotton through a compactor as a stated part of the finishing process; a bargain single-jersey blank skipped straight from knitting to cutting will often shrink a visible half-size after two or three washes, tightening across the chest right where a print sits. The fabric isn't lower quality cotton necessarily — it just never had the loops set before the shirt was sewn.

Spec compacted goods any time the order is a fitted or retail-cut style, because a customer who loses a size to the dryer is a customer who emails for a reprint. It matters less on boxy, oversized cuts that were drafted with extra room to begin with — a size's worth of shrink allowance is already baked into the pattern.

Don't confuse compacting with combing. Combing removes short fibers and impurities from the raw cotton before spinning; compacting happens to the finished knit fabric afterward and has nothing to do with fiber quality. A fabric can be combed and still shrink badly if it was never compacted.