I had a pattern in a mould that I believed was mechanically locked. Since all was lost, I wanted to remove the pattern and do a thorough postmortem. 

Do you have a photo to look at?

https://www.dropbox.com/sh/yb7qpd8ehtkt4mq/om7zUaxPE4

I see.

wipe the general area with acetone, then apply some glecoat, maybe in a cooler temperature. Make sure it gets in the crevices. Put a bit of cling film over it so it cures hard. On the other side, back it with some glass. Once cured, flat it back.

Thanks I will get cracking on this when it's a little cooler. 

Depends. If its quite a straightforward, flatish shape, you can get away with 20mm. The more complex the shape, the more the cloth will have to drape, pull, expand and contract. This makes the excess material vary quite a bit, you hac have large bits hanging, which will need relief cuts. For these shapes maybe around 50mm. If its infusion, 100mm or more.

Thanks Carbon I should have enough room - hopefully...

Hi, 

What happens is the wax in the additive comes to the surface of the gelcoat forming an airtight barrier thus the gelcoat can fully cure hard.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant