Hi, this mould is made from high temp epoxy and oven for 17 hours following the data sheet. 

I think I could of took more care in mould prep which didn't help. But it had about 8 coats of easy lease and struggled to out. Now the mould has carbon print through and cracked gel?

Carbon use xpreg xc110 oven cured following standard curing cycle.

Edit : carbon was in the mould over night before going in the oven as it was getting late and could fix leak in the bag.

Using the sealer is just one more layer of insurance in the whole process. I imagine there is one as all semi permanent release systems seem to have one and they are recommended in their application instructions.

The major enemy in moulds is often that they may not be cured properly, simply a slightly uncured mould material will then try to bond with the new part  being made. By this rational an old mould could be the best for release while new moulds are far more likely to have a stickup.

https://www.rexco-usa.com/why-molds-stick/

For pre preg moulds I will also run the mould through the full temp cooking cycle for some extra curing before using it for the first part. manufacture.