Fabric

Denim

Denim is heavy cotton. It holds moisture, and seams hold the platen off the film. The press has to reach the weave without cooking a rectangle into the cloth.

Heavy-cotton starting points for denim
TransferTemperatureTimePressurePeel
Cold-peel standard160°C (320°F)15 secondsMedium to firmCold
Warm peel160°C (320°F)15 secondsMedium to firmWarm
Hot peel160°C (320°F)10–12 secondsMedium to firmHot
Glitter160°C (320°F)15 secondsMedium to firmCold

The packet supplied with your transfers wins over this table. Where a named film publishes a different press, the lookup shows that example beside the starting point.

Pre-press the area until it is dry and flat. Denim from a cold wash, or folded in a stack, needs longer than a T-shirt. Then press a cold-peel transfer at 160°C (320°F) for 15 seconds, medium to firm, peel cold, and press again under a cover sheet. Firm means the platen meets the weave. It does not mean forcing the handle until the print cracks.

Keep zips, rivets and pocket seams out from under the platen. They steal pressure and they can mark the platen or the denim. A jacket back is an easier panel than a jeans pocket.

Hot peel on denim still wants that heat: 160°C for 10–12 seconds is the starting point, peeled straight away, unless the sheet gives its own time. Glitter follows the cold-peel row and a lighter second press. Stretch denim with elastane is closer to a sensitive fabric. Cover it and test a scrap before you trust the rigid-denim time.

Ordinary cotton notes, including why sublimation is the wrong process, are on the cotton page. Vinyl on cotton is on Heat press settings.

Common questions

Is 160°C a denim chart from a supplier?

No. Xpres say heavier cotton may need a slightly higher temperature and they do not print a new number. 160°C for 15 seconds is the top of the 150–160°C band they do print, held for the longer end of 10–15 seconds. Your packet still wins.

The design failed only beside the pocket.

The pocket seam lifted the platen. Press the flat part of the leg or the chest, or use a pillow under the denim if your press has one, so the film meets the cloth. More heat on a ridge still misses the film.

Sources