A few places, I forget where, mention that bathroom silicone( the stuff in the squeeze tubes that you buy in the DIY stores) can be used as a mold-maker.
Has anybody used this- any tips for using?
Does it work ok with resin being poured into it?

I need to cast some 1/700 helos to bulk out the air wing on my DML Tarawa.

Thanks,
Peter

I've tried once when I run out of proper silicon rubber for my molds. The problems I faced were:
- I couldn't pour it properly (it's much more dense than the one for moulds)
- I couldn't get rid of the air bubbles
- The level of detail was poor
- It tends to break when you extract the pieces you cast
So I had to wait my usual provider to give me some proper stuff...
Ciao

Another solution is to use silicone gasket sealant. You can find it in auto stores and it is usually orange or blue. It is made for high temperature situations so it should be able to handle resin curing. I think the bathroom kind degrades rapidly with heat.

Indeed, I second ModlrMike. I have had some success using automotive gasket RTV silicone. Downside is it stinks to high heaven because it emits acetic acid. It works best for small, one-side casts. Prior to making the mold, you have to coat the master with vaseline or some other petroleum jelly. If you don't, the gasket RTV will stick to the master. I've used it for making copies of hinges and smaller stuff. Larger, 2-piece molds though will be a weee bit of a problem. I tried making a 2-piece mold of a wheel and the mold almost always has some pits produced by air bubbles. This would be filled in with a few gasket RTV applied by brush and the master reapplied. Problem is that even if the first half is coated with vaseline, the second half gets stuck to the first and you'll have to slice it open by using a knife.

Also, the curing time for the gasket RTV silicone is loooooooooooooooong, depending on the amount you use. For the above wheel mold I tried to produce, it took me a week to make it fairly usable. However, for smaller, one piece molds, it'll take a half-an-hour or a few hours to cure.

The stuff has a lower viscousity than regular RTV, so it's difficult to pour. What I normally do is to pour it on the container, then press the master on it. Resin doesn't attack or damage the mold.

To sum it up:

For larger, 2-piece molds, regular RTV is the way to go. But for making small copies using one-piece molds, gasket RTV will do in a pinch.

Hope this helps! :-)

If all else fails White Ensign Models produce all of the types (I think) that you would need:

http://www.whiteensignmodels.com/acatalog/index.html?http%3A//www.whiteensignmodels.com/acatalog/catalogbody.html&CatalogBody[/url]

Peter,

I've used it on a few occasions. And it works well for me. Air bubbles can be a problem but if you prime the original with a thin layer of silicon that should not be a problem. After the priming you can just put a blob on top and smear it al over. I use it for plaster casting of bricks and dragonsteeth. And it gives me enough detail. For instance: the dragonsteeth originals I made from plaster in a woodplanking mold and you can see the planking details in de plaster cast from the silcon mold. Mind you I build 1/72, I need a different level of detail than 1/35.
Make the mold at least half a cm al around, so it is strong enough to be bend to extract the plaster after it has hardened.

Regards, Hut

I just tried to use RTV since I've never casted before and didn't want to make the investment. I couldn't get the mold to come away from the part and now I've got RTV stuck to the resin.

Any easy way to get this off?

Thanks,
Paul

There's no easy way that I know of. You have to gently tease it off the part, cutting, pulling, whatever. Did you use any mold release when you made your mold? If not, then that's what caused the RTV to stick. You can use baby powder, corn starch, or vaseline as a mold release. I'm partial to baby powder or corn starch.

I'll have to try some corn starch next time. I had just brushed on some cooking spray but it didn't work obviously.

Paul