I had to research various types of caulk for windows, and the answer was that I should use silicone (or mastic?). Why is silicone is always preferred when you can remove, can't caulk over it and can't paint over it? Compared to something like Lexel synthetic rubber where you can just redo it without removing old caulk and is more easy for non professionals.
closed as primarily opinion-based by RedGrittyBrick, ThreePhaseEel, isherwood, Ed Beal, Tyson Feb 2 '18 at 15:13
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