Time Temperature And Pressure In Heat Transfer Printing

The Three Variables

Time is the amount of time, in seconds, that heat must be applied to the design and garment. Temperature is the optimal degree at which the design will adhere to the garment. Pressure is the amount of downward force needed when heat applying.

They are not independent. Lowering the temperature usually means raising the time, and a press that is slightly cold with slightly short dwell will fail even though neither setting looks wrong on its own.

Setting Temperature From The Melting Range

The bond line — not the platen — has to pass through the full melting range of the adhesive. That is the single most common mistake: the platen reads 120 C, the adhesive melts at 100-125 C, and the top of the range is never reached inside the stack.

UT-1007 melts at 100-125 C, with flow beginning at 95 C. UT-1290 melts at 105-130 C, with flow beginning at 100 C. Transfer hot melt film works at 140-170 C. Set the platen above the top of the range, then confirm with a wash test rather than by eye.

See Thermoplastic Polyurethane Powder UT-1007

Setting Time From The Stack

Thick fabric, a thick transfer carrier and a cold garment all delay the bond line reaching temperature. A thin polyester jersey and a heavy hooded sweatshirt do not take the same dwell, even with an identical adhesive.

If the garment cannot take more heat, add time. If it cannot take more time, change to a lower melting adhesive — which is precisely why UT-1007 exists at 95 C flow beginning temperature.

Setting Pressure

Pressure closes the gap between the adhesive and the fibres. Too little and the adhesive bridges the fabric surface without penetrating; too much and it is driven through an open knit and shows on the face side. High viscosity grades resist strike-through, which is one reason the polyamide lamination powder is specified as high viscosity.

Cooling And Peeling

Thermoplastics set on cooling, so the peel step is part of the process, not an afterthought. Unless the carrier is specified as a hot peel, let the transfer cool before peeling. Peeling hot pulls the adhesive while it is still open and shows up later as edge lift.

See Transfer Hot Melt Film

A Repeatable Trial Procedure

Fix two variables and move one. Start at the adhesive's stated range, run a small matrix, wash every sample at the customer's cycle, and record the settings that survived. A heat press result that cannot be reproduced next month was not a result.