yep.
do tell them and also send them a fabric swatch.
This way they will print something on it and mail it back to you...sample.
in general, they would need an adhesive base to work at 325-350F low temp, and quick 2-4 sec. press time.... hot peel application. This would make them somewhat stretch resistant and also the quick press time would eliminate some of the problems you may encounter when applying heat to delicate thin light weight knits.
but, they will look and feel like a screen print...sort of.
can't change that.
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