I am using Pol-Ease 2350 Sealer & Release Agent to make sure the silicone (Smooth-On Dragon Skin) does not stick to the mold I have created with Smooth-On Mold Star 15 Slow.

But from the creation of the mold, I have seen that there is a little too much silicone not completely curing between the mold and the original.

Ease Release 200 was recommended by Smooth-On. But, from watching YouTube videos, I though 2350 was also a good option.

Is using the Ease Release 200 something that I should have done? Am I mixing the wrong chemicals?

The mold is now sticky. I was able to create a test silicon part from the mold by using talcum powder to block the stickiness. It worked, but I got the wrong texture.

Any guidance is appreciated.

Ease Release 200 is now on the way (5 days), but If I can figure out how to correctly use the 2350, I can continue with the project.


1 Answer 1


The question describes using 2350 to keep the Dragon Skin from sticking to the Smooth-On 15 mold, but the problem seems to be described as uncured Smooth-On 15 between the mold and the original. It isn't clear from the question what release material, if any, was used to originally make the mold. It sounds like the talcum powder trial was used on the finished mold to cast Dragon Skin. So the nature of the problem isn't entirely clear, and this answer will need to be very general to cover the bases.

If the uncured silicone is Smooth-On 15 that didn't cure when originally making the mold

  • The uncured silicone won't retain surface detail and isn't stable. Demolding will mess up the surface. In some cases, the silicone might eventually cure in whatever shape it's in after demolding.

    Anything you use as a mold release for the Dragon Skin will have unpredictable effects. The uncured silicone isn't a solid surface, plus it might migrate into the solvent in the mold release.

    For these reasons, you're better off removing any uncured silicone before it potentially cures and before using the mold if the mold is still good enough for your purpose.

  • If the uncured silicone is contaminated with something that inhibited its cure, that could potentially inhibit the cure of the surface of the Dragon Skin. So if there is uncured Smooth-On 15 on the surface of the mold but the mold is still adequate for your purpose, that is another reason to thoroughly clean off any uncured silicone before using the mold. Then a suitable sealer-release agent should prevent anything still on the surface from affecting the Dragon Skin.

  • If you used 2350 Sealer on the original when making the mold, there would be reason to question compatibility, and I'll cover that below.

  • If you didn't need mold release on the original (or possibly even if you used some, depending on the release agent), the issue may have been caused by the original, itself. Both of the Smooth-On products are platinum cure, and a long list of materials can inhibit the cure, even in trace amounts. If the original contained any of those materials, or its surface was contaminated with some, that could explain the inhibited cure.

    If you used 2350 on the original, that likely would have sealed the surface, so the 2350 would be what to look at.

  • Once silicone is cured, nothing will "uncure" it. So if you made the mold from the original, and it ended up with a fully-cured surface, any subsequent uncured silicone between the mold and the Dragon Skin casting has to be the Dragon Skin.

  • If the mold is sticky, it isn't ready to be used. Anything sticky is something that shouldn't be there. Adding talcum powder to make it less sticky isn't a good solution. You're just adding more stuff that will affect the surface of the casting. Before using the mold, clean it down to a good silicone surface.

If the uncured silicone is Dragon Skin

This brings us to the key point asked in the question. If the only thing between the mold and the Dragon Skin is 2350, and the uncured silicone is Dragon Skin, could the 2350 be the cause?

According the the manufacturer, 2350 is white petrolatum dissolved in mineral spirits. In the manufacturer's materials I looked at, they say it can be used for casting silicone, and don't mention an issue with platinum cure, but at least those materials didn't expicitly state that it's compatible with platinum cure. That is a point you could ask the manufacturer about, or see if it's mentioned somewhere else. But if it is affecting the cure, there are a couple of possible reasons.

  • One is the mineral spirits. The instructions warn to allow the solvent to fully evaporate before casting. Mineral spirits dissolve not only the petrolatum, but also uncured silicone (and even swells cured silicone). You can dilute uncured silicone in mineral spirits to make silicone paint. It slows down the cure until most of the mineral spirits has evaporated, and a significant amount can't evaporate while it is sealed inside the mold.

    So if the 2350 isn't fully "dry", any residual mineral spirits will migrate into the uncured silicone. Long after most of the casting silicone is cured, there can be a film of uncured silicone at the mold surface, which will take a long time to cure while the casting remains in the mold (and the casting will be ruined if you take it out before it is cured).

    The mineral spirits will eventually migrate farther into the casting and the casting surface will cure, but it will be soft and swollen until you eventually demold the casting, and the trapped mineral spirits can migrate back out and evaporate. But that may also distort the surface of the casting because it will be swollen silicone that conforms to the mold, which will shrink when the mineral spirits evaporate.

  • The other potential cause is the purity of the petrolatum used in the 2350. Petrolatum is actually a pretty crude material derived from petroleum. It is made by separating a range of compounds via distillation. It contains a variable mix of substances that are components of petroleum, and is refined to different levels depending on the application.

    Petroleum contains a crazy number of compounds and impurities. For example, sulfur compounds are a common impurity, and they're one of the substances that inhibits platinum cure. It isn't clear whether any inhibitory substances, like sulfur compounds, would be in the fraction used for petrolatum.

    We don't know how the 2350 manufacturer sources the petrolatum, or what refining steps might be used to ensure that it's compatible with platinum cure (if, indeed, they claim that it is). So unless the manufacturer claims it's compatible with platinum cure, you can't rule out the possibility that it could be the cause of your problem.

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