I am sublimating onto a Sport Tec st700 100% ring spun polyester shirt. Using a medium density foam pad eliminate creases from the transfer paper. The image looks great - very crisp with vibrant colors. My problem is the shirt is discolored in a square the size of the foam pad. I have experimented with temps as low as 380 and duration as low as 40 seconds and I still see the discoloration on the shirt. My pressure is just enough to compress the foam by about one third to one half. When I lift the transfer paper, I see a faint box in the same color as the shirt and equal to the size of the foam pad - the color of the shirt is transferring to the paper. Any thoughts?