Silicone Removal

Discussion in 'Ask A Hunter Owner' started by Breaux, Feb 12, 2018. Add this thread to a FAQ

  1. Breaux


    Joined Feb 12, 2018
    5 posts, 0 likes
    Hunter 23
    Serenity US Mandeville, LA
    I just purchased an H23 and it appears that one of the previous owners got carried away with Silicone trying to protect the insides from water leaks. There is silicone everywhere; all over the deck, windows and even on the cushions in the main cabin. Does anyone know a safe removal process for this?

  2. thinwater


    Joined Mar 26, 2011
    2,306 posts, 559 likes
    Corsair F-24 MK I
    US Deale, MD

  3. CloudDiver


    Joined Sep 8, 2014
    2,541 posts, 421 likes
    Catalina 22 Swing Keel
    US San Diego
    I've done a ton of research on this and tried numerous chemicals personally... Some things seem like they 'help' but nothing I have found is truly effective at removing silicone residue that will be nearly 'forever' trapped.
    When I installed a new shower glass shower door in my house I tried an off the shelf H-D silicone remover (It claimed to break the bond between the silicone and the substrate). I 'think' it kinda worked as claimed, but it just smelled like a standard citrus stripper gel and basically I used a flat razor blade in the standard glass crapping knife to manually remove the residue. Coming off of glossy flat tile it was relatively easy. Still, the gel 'silicone remover' didn't do much.

    Primarily removing silicone caulking is a mechanical process. Use a stiff plastic scraper to get the majority of it, metal is fine if you are not worried about scratching non sensitive areas. Then progress to a razor blade to get the rest, which only works really well on flat, glossy surfaces. You need to get as much as you can off but getting all the residue off depends on the application. If you have to do a fiberglass or gelcoat repair you MUST grind away the gelcoat or glass to ensure there is no trace of silicone residue. If you are re-bedding hardware, manually scrape an razor the old stuff out and bet meticulous about it. If the area isn't sensitive and will be covered you can sand it, but you'll notice the sand paper get mucked up by the silicone residue. Generally speaking, wherever there is silicone residue and I have to re-bed I do so with butyl tape. It will still give an excellent seal and the silicone residue does not seem to hinder it. If you have to re-bed with a polysulfide or polyurethane, that's when you need to grind/sand the surface to ensure you get all silicone reside. There is NO commerically available chemical I know of that you can 'wipe' on the surface of fiberglass/gelcoat that will dissolve silicone residue trapped in gelcoat or laminate pores. DOW apparently does make a product that is supposed to do this but it is only for sale to industrial customers and I'll be it is really nasty stuff. You can find the SDS on DOW's website.
    If you are resealing windows/port-lights that had silicone.... typically, new silicone will seal to cured but clean silicone just fine. The only silicone that should be used for this is DOW 795 and it is NOT expensive, about $8 a tube I think. As long as you manually scrape away the old sealant and razor blade the majority of the film off, new DOW 795 will still stick like crazy, residue in the pores is no concern.
    I am a Practical Sailor subscriber... the article linked above recommends a product called RE-MOV for silicone. Actually, the write is pretty convincing and I want to try it, it may make me re-think my statement that there is 'NO commercially available chemical' that is effective at removing silicone residue. They recommend two applications, 20 minute dwell time, 15 minute interval, then scrape off and use a stiff bristle brush to get after the residue. This might be your ticket!

    My general rule of thumb; NO SILICONE ON A BOAT (for the average DIY sailor); for the above average DIY sailor or professional; there are only a few places on a boat for silicone: DOW 795 for windows/port-lights, appropriate silicone gaskets and sealants for engine/machinery components, and appropriate plumbing fixtures & that's it, otherwise keep silicone off the boat and out of the hands of the un-informed or illiterate!

  4. justsomeguy


    Joined Feb 20, 2011
    6,926 posts, 1,190 likes
    Island Packet 35
    US Tucson, AZ/San Carlos, MX
    A woodworking-type card scraper. @CloudDiver 's right about mechanical means being the way to go here.

  5. Mark Maulden

    Mark Maulden

    Joined Jan 25, 2011
    1,916 posts, 224 likes
    S2 11.0A
    US Anacortes, WA
    Wonder if debond would work?

  6. Hunter Ad Bot

    Hunter Ad Bot

    Joined Oct 27, 2016
    0 posts, 13 likes
    US Seattle
  7. DrJudyB


    Joined Jun 25, 2004
    372 posts, 288 likes
    Corsair F24 Mk1
    003 US San Francisco Bay, CA
    I've used Re-Mov and it works well in a lot of situations, as long as you follow the directions. I don't think it will take silicone off fabric, but it did remove silicone from smooth gelcoat well enough to eliminate fish eyes when I painted over a 6" x 6" area).

    Re-Mov did a very nice job of removing messy residue that a prior owner had smeared in a lot of places on the non-skid on my boat.

    I'll repeat: read and follow the directions. It doesn't work the same was as an adhesive remover. I used a plastic spatula under the edges of thick layers. For thin layers, I used a lot of elbow grease and rough terry cloth rags.

    Last edited: Feb 12, 2018
    Rick D likes this.
  8. justsomeguy


    Joined Feb 20, 2011
    6,926 posts, 1,190 likes
    Island Packet 35
    US Tucson, AZ/San Carlos, MX
    "Hunter Ad Bot, post: 1434703, member: 136017"
    The greatest ad ever.

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  9. Breaux


    Joined Feb 12, 2018
    5 posts, 0 likes
    Hunter 23
    Serenity US Mandeville, LA
    Thank you, I will try that.

  10. twalker H260

    twalker H260

    Joined Dec 2, 2003
    373 posts, 31 likes
    Hunter 260
    CA winnipeg, Manitoba
    As others have said the first part is mechanical removal. After that I have used kerosene and a scrubby or many paper towels followed by cleaning with alcohol or acetone to get rid of the kerosene residue. I’ve done this with enough success to allow fresh silicone to adhere around tubs and to Lino.

    - this should work on most of your solid surfaces, but obviously not on fanbric/soft surfaces. I’m not sure if there would be any issues with acrylics or polycarbonates.

    Last edited: Feb 12, 2018
  11. thinwater


    Joined Mar 26, 2011
    2,306 posts, 559 likes
    Corsair F-24 MK I
    US Deale, MD
    You need to follow the instructions. They've studied it. Don't start with random mechanical removal; this can just make it harder.
    • Exactly how to score
    • Soak time
    • Reapplication
    You can practically peal it off if you do it right, and you can get 100% bond strength afterwords. Really.

  12. bobtigar


    Joined Sep 29, 2008
    155 posts, 1 likes
    Morgan Out Island 33
    US Pompano Beach
    Try staight white vinegar and a stiff scrub brush...not perfect but it dies loosen the stuff too. Bob

  13. Breaux


    Joined Feb 12, 2018
    5 posts, 0 likes
    Hunter 23
    Serenity US Mandeville, LA
    Thanks all. I really appreciate your input.

  14. DianaOfBurlington


    Joined Jun 5, 2010
    983 posts, 53 likes
    Hunter 25
    US Burlington NJ
    EXACTLY the answer I would have given, CloudDiver. I've been doing fiberglass work since 1972 and the one absolute bane to all fiberglass repair, maintenance and construction is the whole presence of silicone sealant within about 20 yards of the boat. In my 45-odd-years of hands-on experience, as well as after having grown up with a yacht-designer engineer for a father (and first teacher), the stuff is the very worst.

    Salient properties of silicone sealant:
    • Has to be mechanically removed, as you said.
    • Almost always requires remedial gelcoat work after removal.
    • Does not provide strength.
    • Does not hold out water.
    • Is always ugly; attracts mold like it's its primary purpose.
    • Interferes with every polishing and waxing job you will ever do.
    • Clogs all sandpaper rendering it worthless for anything else.
    • Soaks into raw wood just enough to bar all epoxy, sealer, paint, etc. from saturation.
    • Interferes with all other adhesion of hardware and sealing of seams.
    • Makes you look like a moronic motorboater (for some reason motorboaters seem to love the stuff; it's almost a black-white distinction-- motorboater : silicone :: sailboater : polyurethanes.

      If anyone comes up with a bona-fide purpose for which silicone is truly the best solution on a yacht, I'll be surprised to hear it (I am not talking about RTV adhesives)

    jon hansen likes this.
  15. Hayden Watson

    Hayden Watson

    Joined Apr 5, 2009
    731 posts, 206 likes
    Catalina '88 C30 tr/bs
    US Oak Harbor, WA
    They don't call it "Devil's Glue" for nothing.

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  16. Gene Neill

    Gene Neill

    Joined Sep 30, 2013
    2,812 posts, 1,421 likes
    C-22, Albin Vega
    US central Florida
    The world simply refuses to learn about silicone. You should see the abominations I encounter in the swimming pool business. I spend many many hours removing it (mechanically). Makes me so mad I can't see straight.


    DianaOfBurlington likes this.
  17. Kermit


    Joined Jul 31, 2010
    5,228 posts, 2,558 likes
    Hunter 260
    US Lake Murray Sailing Club, SC
    Timely thread for me. I just received my used replacement compass today. I used a flat screwdriver to remove residual silicone residue from the back of the collar.

    DianaOfBurlington likes this.