Help making a one time use mold for resin

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**Grass4hopper**

Hi,

EDIT: the main question is can I coat soft clay with a petroleum based or otherwise product to prevent the clay from sticking to the resin?

I need to make some molds for a Gelatinous Cube-like monster that will split and resplit as it's attacked. I'm thinking about just making one time use molds out of soft non-drying clay. My concern is that I don't want to the clay to be stuck to the surface of the resin. If I coat the mold in sculptor vaseline should that prevent the clay from sticking to the resin?

Bonus Questions: I need to suspend some small prepainted items in the middle of these cubes. If I fill half the mold, insert the item, then finish filling the mold do I have to worry about the item sinking to the bottom of the resin? If I seal these prepainted items with clear coat I don't need to worry about them bleeding into the curing resin right? If I add drops of paint washes as I pour, to create milky pockets in the clear cube, will that mess up the resin hardening?

Thanks

**Carlson793**

Silicone bathroom caulk. Loads of tutorials for using it on Google.

**Grass4hopper**

Thanks, I didn't know about that method, that will be useful for future projects.

However I'm not making a mold of a prototype, then casing it in resin. I was planning on sculpting the mold by hand. If that method won't work period, then I'll do the whole prototype/mold/cast method, but I want to know if what I proposed is possible first.

Thanks

**theharrower**

I use Instamold. Best thing about it is that it is reusable. Here's a tutorial I put together for it. http://dedard.blogspot.com/search?q=mold

**Grass4hopper**

That's a useful tutorial, I'll use it for future projects thanks.

However I'm talking about sculpting a mold out of soft clay. There is no original part to form a traditional mold around, I am sculpting the negative space where the resin will go. This should work; the question is: Is then a product I can coat the soft clay in to prevent it from sticking to the resin?

I'm just making seven irregular cubes, so I don't see the point of wasting greenstuff or some other media making originals to make a mold around or wasting the time or materials on creating a traditional mold. If that's what I have to do then fine, but if my proposed cheap and quick mold works I'd prefer to do that.

**MechaEmperor7000**

If this is a one-time use mold then you shouldn't really need a release agent of sorts; after pouring in the resin and allowing it to harden, just submerge it in water until the clay dissolves, then use sandpaper to smooth out any remaining clay particles.

Use the grey looking pottery clay for this. It's the cheapest kind and will dissolve within minutes of being submerged in water. Just be warned that some types of resin can give off heat, which may cause residual water particles in the clay to explode (this is not dangerous, just small pops and the occasional crack in the mold).

Alternatively, if that doesn't sound appealing, try using baby powder. This is the generic mold-release agent for the budget mind (I've used it a few times with latex molds). The only issue is you'll have to thoroughly scrub the casting afterwards to get rid of possible "leftovers" that might cause the transparent resin to fog up.

**Grass4hopper**

MechaEmperor7000 wrote:
If this is a one-time use mold then you shouldn't really need a release agent of sorts; after pouring in the resin and allowing it to harden, just submerge it in water until the clay dissolves, then use sandpaper to smooth out any remaining clay particles.

Use the grey looking pottery clay for this. It's the cheapest kind and will dissolve within minutes of being submerged in water. Just be warned that some types of resin can give off heat, which may cause residual water particles in the clay to explode (this is not dangerous, just small pops and the occasional crack in the mold).

Alternatively, if that doesn't sound appealing, try using baby powder. This is the generic mold-release agent for the budget mind (I've used it a few times with latex molds). The only issue is you'll have to thoroughly scrub the casting afterwards to get rid of possible "leftovers" that might cause the transparent resin to fog up.

Awesome! That's just what I needed to know, thanks.

**MechaEmperor7000**

Just again I'd like to warn you about the heat the resin gives off. If it does give off heat you'll need to find another type of mold material since it will crack the clay mold and can ruin your casting before it sets (and there's no way to solve this, the clay will never fully dry out without being baked in a kiln, and by that point unless you already have access to a kiln you're basically shelling out enough money to start casting metal).

If the resin is that problematic, maybe check out sand as an alternative. That I have never used before, but there's a few tutorials online and it's basically mixing equal parts sand and plaster with some water to allow it to hold it's shape. This will require a master model though, but it should hold up a lot better than the clay (and unlike clay, this will fully dry out so the exploding isn't an issue).

**Grass4hopper**

Ok, thanks. I'll have to do some research on resins. I'll just make the master models if I have to, it just seems a little silly for such simple shapes where I actually prefer some minor imperfections.

**MechaEmperor7000**

An alternative to resin is maybe using hot gluegun glue. It won't be completely clear but it will give that gelatinous look. you can use the non-hardening clay for this and just take a knife and slice off the edges instead.

**Grass4hopper**

Interesting, that sounds like it might be the simplest. Thanks for all the advice, I really appreciate it.

**MechaEmperor7000**

Np, happy casting!