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Itinerant1's avatar
Itinerant1
Explorer
Jan 24, 2018

Removing silicone caulk?

The previous owner used silicone caulk in a few places on the outside trim on the fiberglass siding :(. I've scraped, peeled, slowly and carefully used a flat razor and even gave it good cursing :M yet there is still some that remains is there something else that can be used to remove silcone but safe on the gelcoat?
A while ago I cleaned an area but there was a small amount left, resealed with pro flex but any area that the silicone residue was still there the caulk didn't stay on.
From searching the internet I find "Motsenbockers Silicone Latex Caulk and Foam Sealant Remover" or "Mckanica silicone remover" anybdy use one of these on the gelcoat fiberglass?
  • I've used Motsenbocker's and also, 3M Caulk remover with good success. I had a terrible mess on my aluminum roof, 40 years of previous owners trying to seal leaks (mostly from under the aluminum trim edge).

    I found the best way to use these products is to mechanically remove as much caulk as possible without blemishing the surface. Then apply the removal product to the caulk remaining and cover with plastic wrap so the remover remained liquid and didn't evaporate. I typically left the remover on for a few hours but letting soak overnight worked the best. After a night of soaking, most of any remnants came off with a wipe or tug. Finally, I used a rag soaked with mineral spirits to remove any remaining film.

    The roof trim was eventually covered with Eternabond tapes and the siding joints filled with Geocel Tripolymer caulk (similar to Geocel Proflex). I haven't had a leak in years and the Geocel Tripolymer remains sound and bonded. If I had applied more silicone based caulk, I would be peeling and replacing constantly.
  • I haven't used the two products you mentioned but if it's not a painted gel coat I have used acetone with limited success. It doesn't work well if the silicone is thick.

    I use plastic putty knives to keep from scratching the glass. Once it's mostly scrapped off, I scrub with acetone to remove the film.

    With the plastic putty knife, when the edge gets messed up, you just touch it to a smooth grinding wheel to re-surface and your ready to go again and again and again.
  • The problem is even if you remove all the visible material, there is still trace amounts there that are near impossible to remove and yes, they do interfere with most other materials bonding.

    You may as well try the products listed.
  • valhalla360 wrote:
    The problem is even if you remove all the visible material, there is still trace amounts there that are near impossible to remove and yes, they do interfere with most other materials bonding.

    You may as well try the products listed.
    True. On my TT roof there are standing seams that previous owners filled with caulks and even roof tar. I mechanically removed 98% with a wire cup brush on a grinder. I followed that with mineral spirits, and finally, lacquer thinner. Acetone would have worked as well for a final solvent but I had the lacquer thinner at hand.

    3M caulk remover made a believer out of me. Applied correctly and allowed to work, it dissolved nearly all the caulk over some very thick beads of silicone. It's easier to operate a rag than a grinder, trust me.

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