Making Paintable -- Silicone Caulk (non-paintable)

Model Railroader Layouts and layout building
1

I really did it to myself this time!

I am building a model railroad in my attic. The sloped attic ceiling requires that I use a very short hardboard backdrop. So, I thought that I would continue a painted backdrop sky onto the first 16 inches of the sloped ceiling. To make more gradual the transition from the hardboard backdrop to the ceiling, I nicely sculpted silicone caulk (supplemented at a few locations with some lightweight spackling).

The surprise came when I attempted to prime all of this yesterday. I found that the silicone caulk is not paintable. I thought that I read differently a few weeks back, but I must have been mistaken. I eventually was able to glob the primer on it, but it started to come off when I sanded it 16 hours later in an attempt to smooth out the globs.

Is there any sort of adhesion promoter that I could spray on the caulk which would permit the primer to grab? Page 36 of the April 2006 MR reviews a plastic adhesion promoter.

Alternatively, perhaps, I could apply a thin coat of lightweight spackling with my finger tip. Or maybe, since I was dealing with gobs of paint, I should have waited several days for the paint to dry as a hard shell before sanding.

I would much appreciate suggestions as to how I should proceed from here.

2

Not much of anything will stick to silicone once set, not even more silicone. That’s why it’s an excellent mold making material. You were suppose to use siliconized latex caulk (or just plain latex caulk) which is paintable. I see no way to fix this and it’s gonna be a PIA to get it off. I hope somebody knows a trick I don’t. :frowning: Fred

3

I paint houses for a living, had this problem after the homeowner caulked the baseboards with silcone caulk. Go to a real paintstore and ask for a alcohol based primer. It drys so fast it shouldn,t seperate. just don,t slop it on to get it to cover. light coats should do it.
glenn

4

Glenn, This worked like a charm. Thank you.

5

or if you want to just remover the caulk use a product called xylene, available in the paint section @ HomeDepot, wipe it on the caulk with a rag, then wait a minuteand start wiping off the caulk, real easy to do. (wear gloves and open a window) [;)] I also paint houses.

Have fun & be safe,
Karl.