Heather Fabric

Every third order in this business asks for heather gray or navy without knowing what actually makes it a heather: the yarn is spun from a blend of dyed and undyed (or two differently colored) fiber stock, so the mottled, flecked look is built into the thread before the fabric is even knit. True 100% cotton versions exist, but they're harder and more expensive to produce, so most of these colors on the rack — Bella+Canvas 3001, Next Level triblends — get there through a poly/cotton or poly/cotton/rayon blend instead.

Buyers rarely think about the fiber content behind a mottled color when they pick it off a swatch card, but it changes how the shirt takes ink. Poly content raises the risk of dye migration — the polyester's disperse dye bleeding up into plastisol under heat, most visible as a pink or gray cast bleeding into a white print on a heather red or charcoal shirt.

Pros spec low-bleed or low-cure inks and drop the cure temperature slightly on poly-heavy heather blends specifically to control migration, and they test a swatch before committing to a full run of any new color, especially reds and darks. A CVC or tri-blend version needs that same caution even more than a straight 60/40 poly-cotton tee.

The mistake is picking a shade purely for the mottled look and skipping the fiber-content check — a customer who loves that faded, flecked gray but ignores that it's 50% polyester can end up with a discolored print three weeks later and no idea why.