How to cast resin items in a two-part mold?


Well-Known Member
I really don't want to ask what I am about to ask because it makes me feel like I have no business being on this forum. Please please keep the berating of Groone to a minimum. :behave

I've been sculpting plaster for a while off and on (nothing good enough to post pictures of, just for my pleasure) and I want to try a different medium. Plaster is easy for the first few days but once it starts to cure it becomes a real pain so detailed work is real difficult. I want to change the medium and I see some people using a clay, or clay type compound. What is the best to use that remains malleable over several days to a week to which I can create a mold from?

I have been reading tutorial after tutorial after tutorial after tutorial on how to make a 2 part mold. I think I have the one part mold down pat thanks to the wonderful RPF staff and their video tutorial but the two part to create something like a helmet escapes me.

Most tutorials I have seen stop with the person pulling out the latex mold. I want to see how that is used again to make a helmet. I know about dividing the helmet so it pulls from the mold and how using the release on the keys so they don't stick. How do you pour the resin into the mold to make a hollow shell of the helmet? Do you have to pour it in and then keep manually turning the mold until it dries so the resin doesn't collect in one area? I would love to see a video tutorial of a 2 part mold creation and reuse of that mold once the initial hollow object is made.

I find you guys to be brilliant with your sculpts and creative abilities and any information that you offer I will take to heart and keep with me for a long time. Thank you.


Sr Member
I would either rotate it (would be painful) or make a mold of the inside of the helmet and then insert that into the exterior mold and hang it so the resin can flow between the two. Baby powering the molds will help break the surface tension of the resin and mak it flow smoother.


Well-Known Member
I've seen a couple really detailed videos on youtube about the process. They weren't easy to find and I don't even remember what I searched for (just kept clicking on similar videos until I got something). Just keep searching for "slush casting" and "roto casting". There was a really good one of a fett helmet that i think was done by a member on here but i cant remember who.

Smooth-On has great mold and cast making videos on the small scale but it works just the same.


Sr Member
Anyone interested in molding anything really should own the book "The Prop Builder's Molding & Casting Handbook" by Thurston James. A little old, but still very relevant.

Also, give the gentle folks at Smooth-On a call. I understand their customer service is unparalleled and they are happy to answer questions such as yours (assuming you're using their products, of course).

Finally, this is by no means a stupid question. I was going to end up having to ask it myself in a few weeks once my sculpt is finished. Don't feel bad - the beauty of the RPF is that folks of all experience levels come together to build the community. :thumbsup


New Member
New to the forum as well and I was wondering the same thing. Thanks for asking the question. And a big thank you to the guys that responded.



Well-Known Member
Irishamericanlad, thanks for the link to the tutorial!

Rollerboi, I'll be ordering that book from Amazon today.


Active Member
Have to agree about the Smooth-On customer service: they are TOP NOTCH and will take the time to answer any questions you my have. They also have awesome vids on pretty well every technique you could name....

Lots of ideas and ambition, growing skills...
Learning the ropes and trying to apply things as I learn...


Sr Member
When it comes to slush casting you'll also find that not all resins are created equal. Ones with shorter cure times (or pot life) are preferred, because it means you won't be rolling that mould around for ages. Some resins also cure more progressively than others. I remember from using smooth on stuff that the 300 and 320 series had very similar pot life times, but the 320 cured much more progressively. The 300 was liquid, liquid, still liquid...solid. It made for some very unsightly thick lumps inside a cast, while other areas were paper thin.

And I'll recommend Smooth-ons customer service too, but many other places are equally helpful.


Sr Member
Beaker, I just want to throw another compliment Smooth-On's way. I actually swung by your headquarters/warehouse last week to pick up an order, and even though it wasn't the biggest order (Far from it) everyone I met there stopped and talked to me about my project, and were just really awesome people in general. I've also called customer service about specific techniques and your crew there was an amazing help. It's really a nice change of pace for guys like us to be able to talk about what we're passionate about and get help, rather than the bemused looks we get at a place like Home Depot when we try to explain what we're making.

You guys rock! I'm definitely going to be picking up my future orders in person.

Here's the one picture I sent to my prop-making friends to tease them about my visit:

1233952_669042237355_892643785_n.jpg took a lot of self control not to just run around the factory floor though, there was just so much to look at and I wanted to see it all. :lol

Seriously, if there is something that Smooth-On's team doesn't know, it's not worth knowing.

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