Molding clay
 

Can anyone tell me if you have usesd clay from local hobby shops .. Was wondering if i can get something that will work locally for molds.. Or do u recomend the mold clay fiberglass co sell..materials will be here tues so i will be building decks soon.. Thanks martin

Hobby shop clay works as long as you don't get the kind that hardens when you bake it. It can be hard to find the old style oil based clay, but it works just fine. Make sure to get good coverage over the clay with your PVA or the oil in the clay will cause your gelcoat to alligator.
Dave

I like Permoplast clay.

http://www.hobbylinc.com/htm/aac/aac90055f.htm

strick

Thanks guys...

What is the temp rating of this stuff thanks MJ

temp rating for what?

strick

Clay
 

Of the clay.. Or am i digging to deep for info . Trying to find an equivelant .. I have some @150f... Wondering if it is the same

I'm not that much into it. I'll take a look at the box to see if there is a temp rating. I just put it on the mold and glass over it :)

strick

If it has a temperature rating on it, it's probably of the polymer thermoset type I was talking about. You want the oil based stuff that doesn't set when you bake it. The thermoset stuff will work, but the oil based clays are a lot easier to work with.
Dave

I have been told that you should use a low sulphur clay when making silicone molds. Do not know if there is any reason to apply this advice to epoxy or glass. Sulphur in the clay can effect curing of silicone.

Yes
 

On the right track, it should be a NO sulpher, especially if using a polyaddition/platinum cured silicone. It will definitely cause cure inhibition and you will havea sticky freaking mess, and nothing will solvate unreacted silicone. Isopropyl alchohol will help with wiping up the mess but you will have to use many cloths, papertowels, wipe once discard, repeat, repeat, repeat. if you do not you will just transfer to many other places and you will not get rid of it. if it ever ends up on a surface to be painted or gelcoated, you will have an adhesion issue.

Klean Klay is a commonly used clay which contains no sulpher.

No temp rating on the box. As mentioned previously it's a non hardening clay. I get it from Composites One.

strick

Thanks guys ... Appreciate the advice.. Starting the decks this week..