Opinions differ, but the overriding consensus among carpenters seems to be that painting silicone caulk is not recommended. Silicone caulk is formulated to be used in places where water may be a factor, such as between tub and tile in a bathroom or between a splashboard and tile over a kitchen sink. Because the silicone in the caulk causes it to be slick and slippery, it’s hard for paint or primer to adhere to silicone caulk.
If it’s too late and silicone caulk has already been used in an area you wish to paint, here are some tips to try and make the paint and/or primer adhere to it:
- 1. Rub the area with denatured alcohol. Alcohol has a tendency to rough up the surface of silicone caulk, and this might allow paint and primer to adequately stick. Use oil-based paint and primer (as opposed to latex) for an even greater percentage of success.
2. The other alternative is to clean the silicone caulk very well and then cover it with a thinly spread film of painters caulk and allow it to dry thoroughly before applying paint and/or primer.
3. Chances are, if you’re dealing with silicone caulk, you also face a problem with the caulk and mold growing on it. This black stuff will come right through paint and onto any kind of caulk no matter how much denatured alcohol you put on it. You can purchase silicone caulk with a fungicide in it, but this provides only a temporary fix. Since mold grows not only on the caulk, but also on the soap scum and other unknown agents adhering to the caulk, it’s next to impossible to prevent mold. You can get rid of it, however. The answer? Apply bleach at a ratio of ½ cup to one gallon of water and spray or brush on, leaving about 15 minutes. Be sure and provide plenty of ventilation to avoid inhaling bleach fumes.
The bottom line? Think about where the caulking is going to be used and whether or not water will be present at any time before deciding on which caulk to apply. Remember to use silicone caulk for damp or water-prone areas and latex caulk for all other applications. And if all else fails with silicone caulk you’re trying unsuccessfully to paint or prime, you can always dig it all out and start over.