Funky designs on FEP

[Dave64]

The last 2-3 tank cleans I have done left these funky designs on the FEP. I changed to new epax nFEP, which I have used in the past with no issues, but these new sheet are the draggiest, stickiest most static prone FEP's I have ever used. My print's come out fine, but the tearing noise when the build plate lifts is almost unbearable. Even PTFE makes little improvement. anybody else ever come across this before ?

[billtodd]

How thick is the film? ISTR the Saturn FEP is a um or two thicker than used on the mars . I wonder if the sound is different ?

[Dave64]

.125mm on the thickness. I thought maybe it was a static charge left over creating the designs, but that seems to go away after the PTFE treatment. Before that, on a clean/ dry FEP, my microfiber just drags across it with a scratchy sound and there is so much static that the microfiber sticks to it, even when flipped upside down. The FEP could just be a bad batch, my last set worked flawlessly for months and never acted like this.
Sound wise, all my FEP's hit 300-320 hz on the meter and they all do the same thing.