Hey everybody,

  I have been practicing casting Platsil gel-10 and Ecoflex-30 and have run into an issue with the casts seeping oil. At first the cast appears great and seems to have cured fine, but after leaving it out of the mold for several hours it accumulates quite a bit of oil on the surface. I've wiped it off several times but it keeps seeping out.

 I tried a test cast using my mold and only platsil gel and the cast did not seep oil. This gives me some confidence that my mold is not contaminated. I also tried a test cast using only ecoflex and it did not seep oil (though this was not done in my mold, but in a cup). The issue SEEMS to be when there is a Platsil gel-10 skin backed with ecoflex30. Like te ecoflex is leeching oil only through the platsil gel skin

  I'm not sure what I've done wrong, here is what i'm working with:

  My mold is made of ultracal30. The mold came out rather porous, causing the silicone to stick so I brushed on a little Johnson's Paste Wax diluted with VM&P Naptha. Before casting I sprayed a bit of Mann 200 mold release into the mold as well.  

  I then brushed on two layers of lightly tinted Platsil-Gel thickened with very little Thivex silicone thickener. The cast was then filled with lightly tinted Ecoflex-30 (which i mixed very well to incorporate the solids that settled in the tub).. no retarders or dilutants. 

 Would it be safe to continue to wipe off the oil using naptha, until it stop seeping? It seems to seep less as I continue to wipe it down. Do you think it would accept paint after a week or so of wiping the skin down repeatedly? 


Thanks for reading!

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A couple of things it might be:

The Polytek Technical Bulletin for PlatSil Gel-10 says: "Do not use silicone-based release agents (i.e., Pol-Ease 2300) on surfaces that contact liquid PlatSil rubbers since inhibition and/or adhesion may occur." I can't remember if Mann 200 is silicone based or not, but Smooth-On's website also has Mann Ease Release 2831 which specifically mentions that it's waxed-based. 

Another thing could be Thivex is a Smooth-On product and might not be compatible with Polytek's PlatSil Gels.

Possibly both issues combining to give you problems?


Thanks for taking your time to help,
I did not know PlatSil Gel was incompatible with silicone release agents. The ingredients list contains "a modified siloxane mixture" so this may be my issue. I am running some tests which should show if it is.
Is there any way to remove this spray from the very porous surface of my Ultracal-30 mold? Would brushing it with Naphtha for a while do it, or do you think the contamination could be absorbed into the Ultracal permanently? Would running mutiple casts through it help pull some of the residue away?

Thank you!!

Well, hopefully since you sealed the Ultracal with JPW first, the release should just be on top of that layer and will scrub off with a paper towel. Additional Naptha might let it soak into the mold.

I'm curious to see what results you get, please keep us posted. 

Ok, I did about 15 small test casts to try and isolate the oil sweating issue. 

  I found that the only time oil seeps from the casts is when I have a PlatSil Gel-10 skin painted on, and then filled with Ecoflex 30. I painted a skin of Gel-10 into the left side of the chest area of the mold, and left the right side unpainted and exposed. I then filled the chest with Ecoflex. The cast only seeps oil from the side with the Gel-10 skin. The solid Ecoflex side has no oil leaking.

Even when cast in a disposable plastic cup with no Paste Wax or release sprayed, it leaks oil from the PlatSil skin. 

  There are so few components i cant image where to go from here.

  Its not the ThiVex, the SilcPig, the Paste Wax or the Mann 200 as I was able to cast both types of silicone individually with these components and all casts came out fine. 

  It really seems like an incompatibility with the Gel10 and EcoFlex, but I've seen on this board that people have had success mixing EcoFlex and Gel-10 together so I'm not sure.

 At this point I am ready to try another silicone perhaps.Any suggestions for a Silicone similar to EcoFlex 30?

Are both curing at the same time? Have you tried letting the Gel-10 skin cure first and then adding the Ecoflex afterwards?

I'm not even sure if that's a feasible option for you. 

Hopefully someone operating at a higher pay grade than me will jump in with their thoughts, lol.

  The Gel-10 skin is mostly cured when filled with Ecoflex, but thats a good point and Ill try allowing it to cure for a full 20 minutes or so before filling. I ordered some PlatSil Gel0030 which I will use in place of Ecoflex, I know for a fact that these two Silicones are compatible.

  Anyway, thanks for the help. Ill update if i ever figure it out.

Hi Ross. Sorry to hear about the problems. I haven't tried Gel 10 with Ecoflex, but Nick seems to have had some success with it. I wonder if he applied a lot of coats of Gel 10 to build up a thickness and that might have prevented the leakage? 

What I have used successfully is a skin of Gel 10 and fill of Gel 00 with added deadener. This works fine, as one would expect as all that series of silicone are fixable and interchangeable. Personally I would stick with a single manufacturer rather than trying to combine products not really intended to work together.

I meant 'mixable' but the spellchecker beat me to it!

Hey Simon, thanks for the reply. 

   I have found that the issue only airses when I have Gel-10 adjacent to any other silicone, even PlatSil Gel-0030.  The oil always seeps through the gel-10 side. I haven't tried Gel-00 but i may still give it a shot. I am wondering if maybe my batch of Gel-10 is off, though I doubt it because it was ordered in Feb, has just been opened, and it cures fine on its own.

  Anyway, at this point i'm pretty much resigned to casting the entire puppet in Ecoflex 30 instead of trying to apply a skin of some other type of silicone and then filling it.  Any downside to this? Is the thicker Gel-10 layer of skin essential to prevent wire poke-through?

Thank you so much for taking the time to read and respond to so many threads, I don't know what I'd do without this forum

Simon Tytherleigh said:

Hi Ross. Sorry to hear about the problems. I haven't tried Gel 10 with Ecoflex, but Nick seems to have had some success with it. I wonder if he applied a lot of coats of Gel 10 to build up a thickness and that might have prevented the leakage? 

What I have used successfully is a skin of Gel 10 and fill of Gel 00 with added deadener. This works fine, as one would expect as all that series of silicone are fixable and interchangeable. Personally I would stick with a single manufacturer rather than trying to combine products not really intended to work together.

If anyone else is having issues with oil seepage, here's what i've learned about Mann 200 Spray release and cure inhibition.

 Mann Ease Release 200 is not silicone based, even though the ingredients, and also portions of their website lead you to believe otherwise. An email from a representative confirmed it is not silicone based and works fine with Platsil Gel-10.

I haven't had any sweating from Ecoflex 00-30, or from Platsil.  I've done the same thing, Platsil gel-10 on the surface because it is a little thicker so I get a bit more skin buildup.  Ecoflex inside, because it is a little thinner and pours better (and is softer).   I also mixed the two together once, when I found I didn't have enough of either to fill the mould, and that worked fine.  Maybe it was beginner's luck?  

I did get a lot of oil sweating out when I added some diluent - silicone oil basically - to the silicone I used to fill the inside.  I wiped it off, several times, but it kept on coming out, and after a week of wiping it I ended up stripping the rubber off the armature and casting again.  That's why I switched to Ecoflex to pour inside, it's soft enough without adding any diluent or deadener.  So I don't know why you are getting sweating with nothing added to the Ecoflex.  Unless it's the retarder in the skin, I have never used that so I can't say.

I typed that before reading other replies -

As far as the many coats of Platsil - there are always thin areas or even gaps near the seamline, and that doesn't seem to be a factor, the cast that did sweat oil sweated  all over,even where the silicone had pooled in the low points and was thickest.

 I don't use silicone release agents so I can't say what they might do.  On fibreglass moulds I've used a pva release, a liquid that dries to form a thin film that can be washed off with water.  And I use a mould release wax.  On plaster moulds I just use some soap, shaved off a bar of soap into hot water and mixed, brushed onto the plaster and allowed to dry, and that seems to work for silicone as well as for foam latex.

It does seem a bit weird that Nick has no problems at all with the Gel 10/Ecoflex combination, and you have. Is there a possibility that oil/diluent was added to your batch before you got it? It's about the only thing I can think of.

I have used Gel 00 with deadener as a filler inside Gel 10 skins with no seepage. I also use soap as a release agent.

You mentioned about wire poke-through. The way to combat this is to cover the wire with some of the thin physio foam and coat with silicone, and allow it to set before putting it into the mould, so it keeps away from the skin surface.

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