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Molding Update

Using Smooth-On’s skin-safe mold-making materials, we managed to pull a silicone cast of a baku head that I made out of Sculpey.

Using good ‘ol plaster of paris, we managed to make a plaster baku head.

Conclusion the First: Not terribly easy, not terribly hard. We’ve pulled two plaster heads, one marginally more successful than the other, and they came out…okay. Despite our best efforts, we’ve got air bubbles in the mold that leave blobs of plaster that have to be sanded off, and there were big overruns in the back, so each plaster piece requires extensive retouching with the Dremel and some touch-ups with Apoxie.

Conclusion the Second: This was a stupidly ambitious design. Kevin wants to retry it as a two part mold. I’m going to try another version that involves really cheap silicone caulk, as recommended by my stepfather, and see if I can’t get a more perfect mold.

Conclusion the Third: Barring radical success of those projects, and owing to sheer difficulty of casting this particular design—tapir snouts, who knew?—and all the post-processing required, the Baku at least may be an art-show only kinda thing, where I do maybe three, four, five, with different paint jobs. Since my ultimate goal is to mass-produce a couple of designs sufficiently to offer at the table or on-line…well, still working. I’m gonna have to try something much less insane, like a happy platypus. (Mmm…platypus…)

Conclusion the Fourth: Not entirely sure about plaster. It’s easy to work with, and the end results have a lot of heft, but they’re still kinda fragile objects.  On the other hand, the commercially available resins and whatnot are REALLY expensive. May have to try Hydrocal, which is used to make lawn ornaments, and supposed to be a little tougher.

I can see the plaster working okay for a thing hung on the wall, but not for something that sits on your desk. We’ll see how the painted versions come out…

Originally published at Tea with the Squash God. You can comment here or there.


You are awesome and I wish to marry you and have your kittens. ;)

OK, commercial resins are really expensive. But UrsulaV's art is really valuable. Have faith in yourself: create art that is worth having, and charge what it is worth - allowing for both materials and talent.

I agree - plaster doesn't cut it for a real, like to keep, artwork. But if the materials for such proper art cost, pass it on (and take a fair cut for your talent).

I agree. Make them OOAK out of good stuff and charge appropriately.

Then license it out to a good toy maker and let them work out the, ah, fiddly bits.

oh dear...those are wonderful. I'm afraid of the amount of squee that might happen to me when I see one painted.

the cost of a resin casting depends on a few things, including whether you do a solid or hollow casting. Smooth-cast 65 D is a good roto casting resin that produces nice solid hollow casts. I also add a filler powder which lets me stretch everything a lot further.

How does roto casting work? I've just been pouring in--do I have to, like, swoosh the thing around? (Really...really...new to this...)

3D Ursula stuff!!!!

You do realise people are going to be demanding resin baku ball-jointed-dolls next? 8D

What are you using for a release agent in your molds?

Some commercial "Mold Release" spray thingy from the art supply store.

There's a stuffed platypus in a case with Australian birds, in the museum room at Clandon Park where I'm a steward. It's one of the few things that junior-school-aged children find really interesting inside the House.

Oooo, neat! My aunt used to work with plaster some years ago so I've a soft spot for that sort of thing.

Also, if you're going to mention the platypus, I guess I'll have to inflict this upon y'all...

Have you checked automotive supply stores for the resins used with fibreglass? Should be less than Arty-store prices and, in larger cans.

Oh my god, I could cast it in Bondo!


I mean, depending on the price. I'm...not wealthy.


It would make my stuffed purple platypus happy to have a friend...

"I’m going to try another version that involves really cheap silicone caulk, as recommended by my stepfather, and see if I can’t get a more perfect mold."

I really want to know how this works out (and how to do it). I want to make shoe lasts for my ball-joint dolls and something cheap, local, and in relatively small amounts? Perfect!

If you are having problems with bubbles, are you brushing or pouring the molding agent on? Both can cause bubbles. It's better to dab it on with a brush if you can. Try using a brush on silicon, that allows you do make a mold out of several thin layers. You can see the bubbles, and thus squish them out of existence. Also, are you tapping a lot as it sets up? Tapping will allow the bubbles to travel up and escape.