Painting Over Silicone Caulk Q&A
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In answering a reader question you stated that silicone caulk is not paintable. Might I suggest denatured alcohol on the silicone caulking to be able to paint over it. An old timer taught me that trick and while it may require a few tries this usually does the trick.
Thanks for the suggestion. I always recommend using an alcohol or Wilbond wipe (one of Wilbond's ingredients is denatured alcohol) prior to painting or caulking any questionable surface. I have used it on the residue from silicone caulk and the new caulks seem to stick ok, though it is difficult to know how long they will last and if the alcohol wipe really did any good.
I know alcohol does slightly roughen the surface of latex-based caulks. In speculating why it might also improve the adhesion of paint to silicone caulk, I can only surmise that aged silicone caulk has a slippery residue on its skin that can be removed with alcohol. Then a good oil or shellac primer might have a chance of sticking.
Officially, GE silicone offers no encouragement regarding painting silicone caulk. Though your method might work, I think it's far better to consider paintability BEFORE caulking, and choose a paintable caulk instead of silicone.
There are "paintable" silicone caulks. I've tried them with mixed results. I possible, I suggest NOT using silicone caulk in a place that you may later paint.