the lead or the mix in the clay. I don't see this happening with my binder pages. And I have a few pages w/ all w/o the film in the cardboard. I also have my 2 binders w/ 30 pocket w/ the chip directly touching both sides of the face of the chip. No real transfer. on some few chips the RED is the dominent color transfer on to plastic and w/ chipcos the transfer to other chips (RED) is a real problem. I get the felling the plastic is no so much of the factor rather the chip to any plastic that is it presses against, that is the culprit.