Hi there

i just did a few tests and I have a problem I already had a few days ago without finding the origin.
When demoulding I heard a lot of crrrrrrac (It was extremely difficult to demould) annnnd: 
photos worth more than words: 



As you can see resin sticked on the glass despite the use of chemical release agent so I'm wondering what are the differents possible reasons of this fail.... temperature? too early demoulding? fail when applying the release agent?
something else?

Since I'm here, what's the best way to cut Polypropylene Sheets? I'm thinking about using it instead of glass for the next time.

Thank you mates