Q. Can Exterior Water Seal be overpainted & is it silicone based. A Q. Can Exterior Water Seal be overpainted & is it silicone based. A. Yes it can be overpainted with Water Based Masonry Paint. No it is not Silicone based but Polyoxy Aluminium Stearate. Cromar2020-03-18T15:09:32+00:00 Share This Product. FacebookTwitterWhatsAppEmail