Why has my cast turned out like this?

I moulded my Stargate chevron today using Polycraft DSM Synolite water clear resin DSM Synolite Water Clear Casting Resin - mbfg.co.uk And it turned out like this. The instructions say to use 1%-2% cat so I used 1.5% I stirred the resin for two minutes instead of one but I didn't pour it in to another container like some people suggest. I de-moulded the part after three hours. The open part of the mold is perfect but the cast against the Silicone is all wrinkled but hard. There are two spots on the very tips that are a bit soft. I also used mold release to break the surface tension to release any bubbles. I don't want to try again until I have some idea of what went wrong.

By andy19422 at 2012-07-02

By andy19422 at 2012-07-02

Did you post cure the mold or at least let it air cure for a few days before casting? It may be a reaction with the mold, or the release material. I don't use any release with clear materials, but i only use PU, looks like you are using a polyester product?

i would try again without the mold release, i don't use any with clear resin.

That surface texture is a sign that the resin was inhibited from curing just at the surface, probably by the release agent. Was the release part of a kit with the resin, or was it recommended by the manufacturer? Sometimes these materials are very finicky and simply cannot be used with 'general' type release agents.
Another possibility-is the resin polyester? You might try using more catalyst than specified- not much, say 2 1/2%, and allowing more time to de-mold. The soft tips suggest that not enough catalyst was used and/or it simply wasn't mixed thoroughly.
Molding and casting with resins is a tricky business, it seems like it should be straight forward, but the materials can be sensitive in less-than-obvious ways. I've had good luck talking with manufacturers tech support people when weird things happen, maybe you could try that, too? Good luck!

The mold is about six months old and I don't think I ever used mold release in it. I only spayed mold release on the top of the pour to help release the small bubbles. I will try again using a bit more cat and not spraying the surface. What do I use to clean the mold before I try again in case there is any residue left?

Thanks Trooper that sounds like it could be it. I noticed the piece had shrunk quite alot and was pulling out of the mold before it had set. It has left some residue in the mold, how do I clean it out.

Nice one, Trooper.
You could also try clear urethane resin, 1-to-1 mix, in a silicone mold, and see what that gets you.

For what its worth, it's technically called aligatoring. For those that want to troubleshoot in the future.

Although not accurate, I kinda like the texture.

trooper said:

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i had that exact same problem when trying to cast some clear parts a couple months ago. i contacted the company, i was told to use less catalist..the parts came out perfect then. what was happening was the resin was curring so fast it was shrinking and pulling away from the mold while it was still wet and created that molding effect.

makes sense, thanks for the info.


-z