The easiest and simplest I know of is getting smooth-on's pourable silicone starter kit. Comes with rubber, resin, sealer,mold release, written and DVD instructions. I highly recommend getting the kit and giving it a try, very fun and once you pull a sucessful part (might be the first one), you're addicted.
Madmanmoe gave a good list, though you don't need a scale for the oomoo or smoothcast that comes with the kit I mentioned.
There's plenty of methods, tips and tricks out there, but here's the most basic and easiest I know:
For a basic part with a flat side , use some clay (super sculpey, etc), roll it out flat and level, push the part into it slightlty, then either find something a bit taller than the object and just a bit bigger around (small section of pvc pipe for instance) or you can even take a strip of styrene with the ends taped together and put it around the object and push it into the clay. Your part is now boxed and ready to mold.
I don't think I've used sealer on anything, as it's only needed if the master part is porous. I also don't use mold release for an one part mold most of the time.
With the oomoo rubber in that kit, you just mix equal parts A and B (stir slowly so you don't create extra bubbles) and then pour it into the lowest part of your box. Pour slowly and a thin string, this helps burst bubbles while pouring. The rubber has a low viscosity (for rubber) and will self level. If you come up a bit short when you've poured it all, just mix a bit more and pour again, it'll stick to itself (the sooner you do it the better). Once the part is well covered tap the sides of the mold box to help release bubbles to the top, where they'll pop.
If I remeber correctly, oomoo has a 6 hour cure time, but I've found a few more hours is better, as it still feels soft to me then. Overnight is great.
Once cured, just removed the walls of your mold box, the clay from the bottom, and the original. If any rubber leaked under the part, just trim it with a small pair of scissors (I use cuticle scissors).
You're ready to mix and pour the resin. I rarely use mold release,unless I have fears of something tearing easily. For a part that will be painted, use baby powder (cornstarch). It doesn't serve as a mold release really, but provides capillary action to help pull the resin into smaller cavities. Sprinkle a bit in, brush it around, dump it out, then blow it out well. Mix equals parts A and B (mix it well without creating a bunch of bubbles, but don't waste time, it kicks fast), pour it in slowly, then wait till cured (I usually wait 15-20 minutes). Might seem backwards, but smaller parts take longer to cure than larger. Reason being is that the chemical reaction between the two parts of resin produces heat which cures them. A smaller part will produce less heat, so it takes longer. A large dense batch of resin will acutally produce quite a bit of heat.
Once it's cured, remove the cast, clean it with a degreaser if you used mold release, then it's ready to finish.
As for the urethane rubber used for some cowls and mask, I know CFC has said he used smooth-on's vytaflex and I think I recall someone saying they used the reoflex (also by smooth-on) for a mask/helmet/cowl.
great question!
I too have always wanted to 'try' to cast something.. (even mold first if I get ballsy)
....
but never had a clue where to start. I saw some links/kits (starter) mentioned at your local Michael's craft store....
Are there many 'parts' of this puzzle?
1.) build box (learning about registration pints..etc)
2.) buy 'kit'
ow many different chemicals/ingredients are needed?
I see things mentioned like release agent.. and many different 'name' (terminology) that seem to be common in that scene..
Also.. to vary the topic a bit...
what do people use when doing the 'rubber/urethane' type flash/Capt. America type helmets? (brand? type?)
would be fun to take a couple of my kids' toys and cast them to get a nice idea of the process and just learn/play with something new!
thanks!
