Sculpting Surfaces

[deepblue]

What are surfaces that you've tried that worked and did not work? I'd love to know.

If you care to read the reason I've decided to ask this specifically, you can see below. If TL;DR, that's ok, I really just want to see what everyone's used to sculpt on.

I drew my fluke design on tracing vellum, and when I attempted to sculpt on that, it of course didn't work. The clay would not even begin to stick, so to speak, everything just slid around. The vellum I was using is not the traditional 'made from skin' kind, it's a cotton/paper blend that I had a roll of from making my child's Halloween costume patterns.

So I acquired a piece of Lexan large enough to cover the design, and sculpted over the design this way. Sculpting on that went great, because the clay sticks very easily. I could also make a scale and lay it on the Lexan, then lightly nudge it down, and when liquid resin or plastic was poured over it, it stayed put.

However, once the resin or liquid plastic was poured, the Lexan warped. My second go (after my first fluke mold was a fail due to the resin cracking, nothing to do with the warp, really), I weighed down the Lexan and the mold seemed to stay flat. Edit to add: the Lexan returned to a normal, flat shape once the mold was removed, and wasn't warped itself. So it seems to me now that it wasn't the heat that did it, it was the mold itself.

But it didn't; the Smooth-On Smooth-Cast produced enough heat that when it was all done, I had a mold which was bowed up in the middle. I've poured a test, and even evening out that section is not going to work. Dealing with liquids, it of course needs to be even.

I've thought about using a piece of tempered glass over the drawing, but glass being what is is, I'm not fond of that margin for disaster.

I know a lot of people use cardboard, which I didn't want to do because transferring my fluke design onto cardboard leaves so much room for error. But it looks like it might be my best shot.

[Mermaid Fenicia]

(ply-)wood plank => paper pattern => wrapping foil => clear tape

[Mermaid Livou]

Hey Deepblue, Im not sure if my experience will help but tought I would share:
> I made my small fin sculpts on hardwood shelf I picked out from my furniture XD these were stiff and mobile enough to work on it, also my mold came out as flat as it should be.
> My fluke sculpt, hence big, I made it on a plywood(?) 120 cm x 120 cm. Stiff enough, but still, my mold became bent when fully cured.
>> Small ones came out flat, big ones become bent. So I guess these matrials are not suitable for big surfaces, I mean they bend a bit regardless of what is the base u sculpt on :/ or if its too thick (if some parts of the design is higher) coz the more material I need for a bigger mold, the more noticable and annoying the shrinkage of the resin will be and bent itself. Or im just a resin-bender D
For me even using fiberglass cloth (to strenghten the strucure and use less resin so get thinner mold) didnt work out, still bent the mold, plus the cloth's pattern went trough and became my mold's main patern -.- yeah, I guess thats why mold-making is a separate profession too
(Oh, however, I worked with epoxi-resin, not with a smooth-on product.. the very first time I made a small mold, but was too thick, the resin started fumigate and kinda burn o.O )

hope U find a solution

[Marinus Mortimer]

I sculpted and molded ( in plaster ) in regular blank papers taped together and I drew my design/outline on the paper then sculpted on top


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[Mermaid Wesley]

Oh! I taped my fluke design to the back of a sheet of plexiglass from home depot It worked swimmingly and my shell shock doesn't stick to the plexiglass. I would still use mold release but yeah! That works! I have only cast my small fins on the plexiglass though, I havent done the fluke yet, so I cant tell you if it would warp on a large scale.

[deepblue]

I really like the idea of plexiglass.

I'm mostly concerned about this warping issue now, I wonder what is up with that. I'm going to do more research about that... otherwise, I could be looking at another warped fluke mold in my future. Do not want.

[Dancing Fish]

All of my large molds are a little warped. For the last one, I stuck a weighted board on top of the smooth cast mold after it hardened to white but while it was still warm, and that helped with the warping a bit.

[deepblue]

^I'm going to give that a go with my warped mold. It's just sooo bad though. Still, nothing to lose.

FYI, since I started this thread and mentioned Lexan, I think I ought to put this here. I mentioned it in my tailmaking thread. The culprit in my fluke warp was Lexan. I used a Lexan sheet to sculpt on and pour the mold, and Smooth On explained why that didn't work, which is in my thread if anyone needs more info.

Moral of my story is don't use a Lexan surface to pour Smooth Cast onto.

[Dancing Fish]

I've used wood, cardboard (don't!!), particle board, and big sheets of wall paneling as sculpting surfaces...all of my big molds are at least a little warped. I just clamp them flat to the work table with C-clamps, that also works...as long as your table is also level... I think there's also a small amount of shrinkage that occurs with Smooth Cast, which only shows up in really large pieces. You should have heard the CRACK-CRACK-CRACK as the mold separated itself from the particleboard backing as it cooled. (Note: MOLD RELEASE. LOTS OF MOLD RELEASE if you're going to use particleboard...saran wrap works too) Cardboard was the worst. That was a really small mold, but it still ended up bowed up in the middle.