Problems painting silicone mask

Gizmo

Hi! I'm having some huge problems with my silicone masks and I though I could get some advice here. I've been painting masks for a few years now, and everything has worked fine until now. I cant get silicone paint to cure at all over my masks (its not a problem with a single mask). I use a mix of naphtha, smooth-on pigments, and either plat-paint or silicone caulk. The mask is made with platsil gel 00. The problem Im having is that, if I apply unthinned silicone on the mask, to fix some spots, it will cure with no problem. But if I thin the silicone (any silicone) with naphtha, then it will remain a slurry mess for ever. However, the one in the cup does cure perfectly!

As I said, it happens both with platinum silicone painting base and silicone caulk. I've washed the masks properly with soap and water, isopropilic alcohol 99.9% and naphtha. Silicone caulk cures on the mask if it goes unthinned, not at all if I thin it. I've painted lots and lots of masks in the past with success, but none of my masks seem to accept any paint now. 

Any idea of what I might be doing wrong?

Micah J.

Try switching from naphtha to NOVOCS gloss. It is a silicone solvent made by Smooth-On. It works well with both platinum silicones being used as paint and also acetoxy-cure silicone adhesives ( most of your standard silicone caulks ). 
We use a mixture of 4 to 1 milliliters of pigmented NOVOCS to SilPoxy ( smooth-on's silicone adhesive) and it is cured to the touch in about  15 minutes although, I would wait longer for stretching the silicone mask. Once cured, you would be hard pressed to get the paint off with a belt sander.
Also, make sure the alcohol is completely flashed off the mask. Alcohol will inhibit the cure of platinum silicones and acetoxy cure silicone adhesives. 

Gizmo

"Alcohol will inhibit the cure of platinum silicones and acetoxy cure silicone adhesives. "

I think this might be the problem, I've only reciently started cleaning the masks with alcohol since I saw it in a tutorial. NOVOCS matt I've used, with success in the past but its not currently working. Maybe my masks are ruined by how I use the alcohol. Thanks for your advice, I'll make some tests to see if not using alcohol fixes the problem

Jeffrey Warren Park

It definitely sounds like an inhibition problem is occurring. It might be a matter of your current supply of naptha being corrupted somehow. Is there any latex, (such as latex gloves), around where you are working with your silicone(s)? Are the tools you are using to paint with thoroughly clean? When cleaning the mask/silicone casting are you using distilled or tap water? Tap water can carry several pollutants that can keep silicone from curing right. If you have used your isopropyl alcohol to clean anything other than silicone, contaminants may have migrated to the bottle. If you use sponges in cleaning the silicone and/or painting process, are any of them latex?

From how you are describing your problem(s), something in the application and/or thinning of your paints is corrupted somehow. I think the only way you'll track it down is through methodical process of elimination. Unfortunately, there is no easy, obvious answer to give you.