I have run into an issue recently, I used an auto primer to cover my masters. I tried a paint that was a primer/filler and it caused issues with curing. Is there a recommended brand or type (acrylic, enamel, lacquer)?
It depends on the ingredients in the paint - platinum silicones are a bit picky and are sometimes easy to inhibit on the curing. I recently found out (the hard way) that Flex 30 has a tin catalyst and will cause Plat 25 to not cure - I was using Flex 30 to cover the bottom of a mold box around RC-3 resin castings and the Flex 30 caused the Plat 25 I poured over it to not cure. The Plat 25 cured over the RC-3 castings just fine (I painted the surface first to reduce bubbles) but everywhere else, it refused to cure - it at least cured enough (around the RC-3 castings and mold box sides) to get the Plat 25 out of the mold box but that was all. It was inhibited enough to not fully cure over half way through the mold and stayed a "gummy" looking waste. I tossed it right in the trash and cleaned up the mold box and castings thoroughly in addition to removing every scrap of the Flex 30.
If you can, I would skip the paint if the masters are made from resin or some type of plastic or metal. If that's not possible, then I'd switch to trying one of the tin cures like HS-1,2,3 or Amazing Mold Rubber. I've had good luck with using HS-2 in a baked clay mold and not having any issues with curing. And the baked clay wasn't sealed either. Also when I have to paint a resin casting, I use Krylon paint/primer which I believe the HS silicones don't have a problem with. My masters are usually resin and I use baked (unsealed) clay when I'm making a mold for resin castings.
Usually most primer paints work well with most Alumilite mold materials and the Platinums are picky but the Tin cures shouldn't have a problem. Try switching the type and let us know how it works out for you, I for one would like to know if there are any problems. I have yet to see a difference in the detailing picked up between the Plat 25 and HS-2 (as I work with both) so you should be okay to switch over without losing any details. I have a feeling it's the filler part of your paint that caused the problem.
And I knew I had instructions on what kind of paints to use in the molds - just had to do a little looking to find it:
"Fast drying lacquers or acrylics (synthetics or enamels also) can be used to paint the inside of a mold."
Now that does apply to a finished mold when you cast resin in it so it may or may not apply to what you need right now but it does add a little information that might help you later on. So again, I'd switch to the tin cure silicones and see if that works better with your masters.
Sorry for the delay in getting back with you. My issue with Tin cure silicon rubber is shrinkage, but I may not have a choice. The tolerances I use are important because I use an o-ring to seal the cylinder from water. A small amount of shrinkage can cause inconsistency in sealing. That being said, I can make the groove slightly less deep to make the o-ring seal harder to the cylinder. Thank you for your suggestions, I will take them to heart.