Problems with kiln paper

[Muskito]

Hello,

I did not have the problem of the paper curling, but I did have 2 other problems:

1) when the corners of a square piece retracted, it picked up the merky white stuff.

2) all the pieces had picked up all the residu powder on the side that was on the paper. So the transparency looks dirty.

Any ideas on how to avoid this and how to cure the problem?

Muskito