URGENT Please help: Wood Filler in Ultracal mold for Silicone Mask

[Egon Spengler]

Well I used wood filler to patch some cracks in my Ultracal mold.

After filling the cracks I noticed something on the package. The wood filler is latex based. I want to cast a silicone mask into the mold.

How screwed am I?

If I seal it over with Krylon Crystal Clear or Shellac, will it keep the wood filler from inhibiting the silicone? Will latex based wood filler even inhibit silicone to begin with? I know that you are supposed to keep latex and silicone apart. Does the wood filler even have enough latex in it to inhibit the silicone? Is my mold completely useless for making my silicone mask now?

I'm fairly certain that years ago I used the same wood filler to fill cracks in another mold for a silicone mask and had no issues, but with a deadline closing in, I'm kind of freaking out here. Either way I have no choice but to try to seal it under clear coat and try to get a silicone pull from this mold.


Please any advice or information would be most welcome.


Thanks!

 

[animator]

I wish I had an answer! I would suggest sealing the area with clear coat and spot testing it with a small batch of silicone.

If it's Smooth-On silicone, I would also suggest calling them for advice. They are super helpful. Good Luck!

 

[Egon Spengler]

animator Well, it seems like it all worked out. I sealed it really well and I didn't have any issues

 

[animator]

That's great! So much time and work gets invested in a project. Issues with a mold are scary.

 

[JRFerreri]

Something to be aware of is that "latex" is a category, not a single material. Latex simply means a stable dispersion (emulsion) of polymer microparticles in water.

PVA glue and housepaints are such an emulsion so they fall into the category. Acrylic medical adhesives such as Pros-Aide are latexes. Polyvinyl butyl, nitrile, styrene/butadiene, neoprene, polyurethane and other polymers can be formulated as a latex.

When we hear the term "latex" we tend to think of NRL (natural rubber latex) which is actually cis1,4-polyisoprene. The reason it is incompatible with silicone is because it contains polysulfides.

Sulphur compounds inhibit catalyzation of platinum based silicone systems. Many oil-based clays contain sulfur so you have to watch out for these when working with silicone. Standard NRL surgical gloves can cause a problem, and even antibacterial soap which uses sulfur for destruction of bacteria.

You could call the company and try to get in touch with a chemical engineer there to ask if the product contains any , explaining your situation. NRL is not the only thing that can have sulfides added. No sulphur, no problem.

The next solution is to use a tin catalyst silicone system.

The final solution is to use an inhibition preventing sealer like "Inhibit X" from Smooth-On.

If you seal it with spray shellac, you can just use their standard Universal Mold Release.

Any sealer and release agent should be allowed to thoroughly dry before using silicone.