The folks stretch it while the transfer is hot to open the weave so the tranfer does not dry/cure with the weave closed. Once they open it up with the stretch, they re-press it to re-set it into the fiber.
If you've gotten cracking with the JPSS, it could be because you only stretched and didn't re-press to reset the ink/polymer.
When you say Iron on paper, do you mean Ironall, Jim? Thanks. (Second thread I've seen with that name and I'm really curious what paper you mean.)
I used to use Ironall, and there is no difference in a freshly printed image. The difference for me came out of the washing machine. I did find I could stop the Ironall light from fading by using a Jerzees HW 5050 shirt (29), but the others faded, and some miserably. I tested FOLT, Anvil, Gildans, Hanes, the Jerzees of course.
Are you using a new version of Ironall paper, or some of the new batch of the regular old version? Thanks.