Casting fibreglass from fibreglass mould?

[JANDERS10]

Hello,
has anyone tired this, or know of any good release agents so I don't just end up with one solid lump of fibreglass?

 

[Zombie Killer]

Does the mold have a gelcoat surface or is it just fiberglass?

 

[TMP]

Depends on the shape your plan to cast from.

 

[CustomPropSculptorGuy]

You're gonna have to have a multi-piece mold. If anything, I've used a couple coats of Plasti-dip as a mold release before.

 

[Pete SSS]

Yeah, it all depends on the undercuts. If there are any at all then your going to have problems. What are you planning to cast?

 

[jedimaster]

I use pva as a release agent in fibreglass molds or release wax.

 

[Holluba]

Personally, I'd avoid pva release at all costs as it's just more trouble than it's worth, plus it's not the best of solutions anyway.

However, I absolutely swear by this stuff:

Fiberglass Supply - Release Agents

Scroll down to the second product on the page, "Honey Wax" in the yellow tin.

I've never had a casting failure with it, you can polish your mould up to the point that it almost looks like glass and depending on the shape of your mould, you can get your casts to just fall out! Obviously the more complex the shape, the more the demoulding time will take.

I've used lots of other products, but having found this stuff, I've never looked back.

 

[fettster]

as long as there are no undercuts, its fine, just wax it and then powder.

 

[JtotheP]

Personally, I'd avoid pva release at all costs as it's just more trouble than it's worth, plus it's not the best of solutions anyway.

I haven't had a problem with PVA--it just takes a good HVLP gun to spray a few good clean smooth layers of it for the best results. I love that it's a water cleanup.

 

[exoray]

A few good coats of plain old Carnauba car wax works too, as said any undercuts and you are in trouble...

PVA works as well but if pulled surface is important it can cause issues if the PVA pools in the mold, or leaves other surface imperfections when being applied... PVA can't be beat as a back coating to the layup though if you are having 'sticky' or curing issues due to humidity and temp...

 

[JANDERS10]

Cheers for the tips thus far.
To respond;
There is no gelcoat, just fibreglass, but that could change.
The shape has no undercuts, and has been designed to pull easily, like a pyramid with the top cut off.
Ta.