Tip Time: Double Casting

This is one of the things I get asked about the most.

How do I double cast something?

Well. That’s easy...

You cast a small thing and put it in a bigger mold. Then fill that with clear resin.

See! It’s easy!

Okay look, I don’t know all there is about double casting. But I will tell you everything that I do know.

I will use my X-Ray R2-D2 as an example for this article.

X-Ray R2-D2 (Matte Finish)

1. Make sure the outer piece is shiny and glossy before you cast it. Put some top coat or some gloss on the piece before you cast it (see my “Finish Him” post for more). This way it will be crystal clear and the inner piece will be visible. The first time I made these, I did not treat the surface and some of them came out a little matte. (See above)

2. Your inner piece should lock in some how. This R2 skeleton is held in place by his shoulders and legs. If it doesn’t lock into place some how, it will get turned around and shift inside the mold. I made a skeleton for C-3PO that did not have a notch to lock into the mold and had to toss a lot of them because the skeletons kept getting turned around in the mold.

This 3PO skeleton shifted inside the mold.

3. The less detail on the surface, the better. This R2 works so well because there is very little surface detail.

It is hard to see all the detail I put into the inner piece for this Dark Dimensions Two Bad because the surface is so busy with the armor and scales and whatnot.

The surface obscures the inside piece.

4. You’ll never double cast into a tiny area. If you want to put tiny fingers into a tiny hand of a little 3.75 Vader... Forget about it. The double casts have to be able to fill with the second pour. Of yourinner piece is taking up all the space inside the mold it won’t fill properly. You will just end up with a half covered piece with a giant bubble in it.

Also, your mold should be properly vented. (See my other post on venting)

Prepare for heartache. This is hard. You will mess up a lot.

It is that much harder because you cast one piece. Then paint it. Then load it into the second mold. Fill it up. Then there is a giant bubble in it or the inner piece shifted.

The Dark Dimensions Two Bad was a 2 hour paint job. There was real pain in tossing it away.

The way is do my double casts goes like this.

Cast the outer piece. Then I sculpt a piece that fits inside the mold. I usually close it in the mold and shake it and rattle it around to see if it fits or will shift in the mold. Then I cast it.

Sometimes that piece won’t fit. So identify the problem and fix it then recast it.

I know some people will fill their outer piece cast with sculptors wax then make a reductive sculpture from that. But I have never done it.

I also know of people that sculpt on a 3D sculpting program and just sculpt the inside piece to the parameters of the outer. But I’ve never done it. I don’t know how to use those programs.

There are probably other ways to go about this. But this is how I do my shit.

Good luck with yours.

Got a question about your double cast? Leave it below and I will answer it to the best of my ability.

Also, if you find a better way to do this, please let me know.

Your friend,


P.S. Thought I was gonna make an “Inner Peace” joke didn’t you?

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