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Thread: Why no Silicone???

  1. #1
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    Default Why no Silicone???

    Didn't want to hijack Tallman's thread on bedding SS screws, but want to ask- What's so terrible about using 3M Silicone?

  2. #2
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    Default Re: Why no Silicone???

    No finish, whether paint or varnish, will ever stick to anything that has had silicone on it. No matter what you use to clean it off. Ever. Plus it causes fisheyes in your finish even in places you'd swear it never got near.

    Steven

  3. #3
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    Default Re: Why no Silicone???

    If --*IF*-- you use silicone over relatively new oil-based paint, such as when you misplace your brain, forget about silicone's repulsion of paint, and you use silicone to stop up a leak at the cabin trunk just to get you through the rest of the season, and you later sand that paint THOROUGHLY, new paint will stick to it, but I suspect that in that situation you've pretty well sanded away the silicone residue.

    Not that I'd know anything about that personally...

    Otherwise, yeah, better save the silicone for sealing the terrarium back at the house.

    Alex

  4. #4
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    Default Re: Why no Silicone???

    Don't go there. Just don't...
    "The enemies of reason have a certain blind look."
    Doctor Jacquin to Lieutenant D'Hubert, in Ridley Scott's first major film _The Duellists_.

  5. #5
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    Default Re: Why no Silicone???

    Products going to the automotive manufacturers assembly planes typically have specific notes on the drawings that "no silicone may be used in the manufacture of this product" for exactly this reason. it causes heck with the painting and finishing processes, and once introduced gets everywhere .

  6. #6
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    Default Re: Why no Silicone???

    I have mechanically removed silicon and then used Silicon remover, and applied epoxy over. It worked fine. They use silicon remover then painting cars. But it is a very expensive blend of chemicals.

  7. #7
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    Default Re: Why no Silicone???

    Why not? This. Silicone bedding under the skeg, totally separated from the keel. Trapping water, critters, and gunk under there:



    But go for it, try it and see for yourself. Only takes a little while to fail. If you keep after it, you can catch it before it rots, replace it with real bedding compound.
    Chris
    ____________________________
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    Tern, a William Atkins Pixie. Builder: Jeff Stobbe, 1997. Completed restoration 2016
    Sparkle, not a Herreshoff 12-1/2, same but stretched to 14-1/2. Builder: Jeff S, 2013.

    Previous: Ydun, Folkboat US 88, owned 1997-2000 ish, Berkeley, CA Sailed her one weekend, worked on her the next. Builder: Borresen, 1950 (Denmark)

    Spokane, WA.
    Row, sail and sleep on the beach around Lake Pend Oreille, usually near Garfield Bay, Idaho.

  8. #8
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    Default Re: Why no Silicone???

    Except the real compound won't stick where silicone has been.. Ever.

  9. #9
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    Default Re: Why no Silicone???

    I'm sensing a theme here....(is it possible that this is the first example of unanimous agreement in the history of this forum?)




    middlething.blogspot.com

  10. #10
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    Default Re: Why no Silicone???

    It's good for caulking bathtubs!

    Well - except that it lifts after a couple of years & gets moldy & gross.

    Now silicone liquid is a good lubricant on casement windows - that you never plan to paint.
    "If it ain't broke, you're not trying." - Red Green

  11. #11
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    Default Re: Why no Silicone???

    Don't even say that word in an Auto body shop.

  12. #12
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    Default Re: Why no Silicone???

    Quote Originally Posted by Hunky Dory View Post
    Don't even say that word in an Auto body shop.
    Unless one is talking about a certain type of enhancement of the female form, of course.
    "If it ain't broke, you're not trying." - Red Green

  13. #13
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    Default Re: Why no Silicone???

    Even silicone won't stick to silicone that has set!

  14. #14
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    Default Re: Why no Silicone???

    We had a wise and sage advisor on things nautical here in S. CA, some years ago. He ran a school on marine licensing for those of us who skippered boats in our area. He was, an ammical guy named Swede Johnson who had a habit of passing out his special award card known as The Dumbsh*t Card. This award was reserved for those of us who refused to recognize both truth and common sense. If Swede were alive today, I believe he would be the first to award his card to anyone who touts the use of products containing silicone for use on or around boats.
    Jay
    Last edited by Jay Greer; 03-30-2016 at 02:45 PM.

  15. #15
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    Default Re: Why no Silicone???

    The Airframe guys at Boeing will shoot anybody with a can of WD40 they see in the build area. Totally forbidden.

  16. #16
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    Default Re: Why no Silicone???

    Oh, come on now, guys... Silicone caulk has its uses on a boat, but it must be used correctly and judiciously.

    About the only use for it I can think of off hand is as a pretty good gasket making material for limited applications. I have never had any problem using it to create gaskets for window glass in wooden rabbets in cabin sides and the like, provided it is covered with a trim piece. Its great compressability and its property of never hardening prevents the swelling of the wood from cracking the glass. It shouldn't be exposed to the sun. It should never be sanded or allowed to smear anywhere that you intend to ever paint or varnish. (Sanding silicone is in the same league with using steel wool anywhere on a boat.) Like lead, if its properties are known and taken into consideration, in its place, it's not an inherently bad thing at all.

    Now give me one of the Swede's cards!

  17. #17
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    Default Re: Why no Silicone???

    I thought it was good for windows too! That is until one day some windows I had installed, on a pretty little sloop, started to leak. Since that time I have resorted to Dap window glazier's putty with no ill effects, indigestion or leaks.
    Jay

  18. #18
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    Default Re: Why no Silicone???

    From a guy who works in the caulking business, keep the silicone in the bathroom.
    Anywhere else, stick to a polyurethane caulking like sika 15lm or dymonic FC if you want something to seal, and paint.
    ...and tool it with sharpened wooden sticks and Palmolive for the best finish.

  19. #19
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    Default Re: Why no Silicone???

    Good to know, Jay. I've never encountered that problem, but I'm taking your word for it.

  20. #20
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    Default Re: Why no Silicone???

    All Anthéa's deck caulking is done with WKT, a silicone based goo.
    Still ok after 20 years (except smalls zones in the cockpit I had to redo).
    When caulking, I take care about masking to not overflow the painted areas.
    This product is fantastic. Never get hard, and follows the wood movements.
    It worth the risk of paint concerns.



    http://www.premapro.com/products/nautichem-wkt-sealants
    Gerard.
    SCHOONER FOR EVER, GOELETTE A PERPETE

    http://www.goelette-anthea.fr

  21. #21
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    Default Re: Why no Silicone???

    Quote Originally Posted by Rob540 View Post
    I'm sensing a theme here....(is it possible that this is the first example of unanimous agreement in the history of this forum?)
    You had to say it, well, type it anyway. You must have known that someone would have to spoil it if you said it out loud, so to speak. Posted it without setting the font color to white? Whatever.
    Quote Originally Posted by Bob Cleek View Post
    Oh, come on now, guys... Silicone caulk has its uses on a boat, but it must be used correctly and judiciously.
    Now give me one of the Swede's cards!
    OK, so there are some limited uses for the stuff, but if you don't speak a language filled with words like acetoxy, oxime, platinum or addition cure and chain scission, it is hard to figure out where and when the stuff will do what you need it to do without contaminating everything in site. There are places where it can work. I have an all glass aquarium that I bought in 1967 that still holds water and is held together with nothing but silicone. I have used it in a lot of places, but not on my boat.

  22. #22
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    Default Re: Why no Silicone???

    The only good use for silicone is bonding and sealing glass to make an aquarium.

  23. #23
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    Default Re: Why no Silicone???

    Only because I did not know any better, I have used silicone on screws that are removed annually. Case in point is flagstaff socket on a varnished taffrail. I have found it easier to pull the screws to revarnish than to sand around the fitting. After sanding and varnishing (two coats), I rebed the socket and screws in silicone. Never had a problem with the varnish not sticking or fisheyes or with water penetration down the screws. What am I missing?
    Dave

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  25. #25
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    Default Re: Why no Silicone???

    Not that this has anything to do with boating but it's interesting all the same. I was once a salesman for a company producing baking equipment. We were marketing a new silicone based release agent for bakeware, which was excellent, but I had one baker reject the product out of hand claiming that his sponges and cakes would not rise very well in bakeware that was silicone coated!! There's obviously something in silicone that is truly insidious.

  26. #26
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    Default Re: Why no Silicone???

    Silicone has its uses. Today Im bonding silicone sponge rubber gaskets to hatch frame. Silicone is used as the bonding glue.

    A very common teak caulking compound is "Teak Deck Systems" brand. This is a silicone seam caulk .

  27. #27
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    Default Re: Why no Silicone???

    Quote Originally Posted by CundysHarbor View Post
    Only because I did not know any better, I have used silicone on screws that are removed annually. Case in point is flagstaff socket on a varnished taffrail. I have found it easier to pull the screws to revarnish than to sand around the fitting. After sanding and varnishing (two coats), I rebed the socket and screws in silicone. Never had a problem with the varnish not sticking or fisheyes or with water penetration down the screws. What am I missing?
    Dave
    You were not sloppy with the silicone. That's what happens when you are very careful. You don't get to experience the same frustration as the rest of us. Silicone is very likely to get on your hands, is hard to completely clean off and will spread everywhere once the uncured material gets out of control.

    It can be a disaster, but it doesn't spread itself around, unless it breaks down. One problem with silicone is that there are so many very different chemistries and formulations. The ones that smell like vinegar can trash electronics because the vinegar (acetic acid) fumes form unstable corrosion products on solder joints. Some break down in hot humid conditions and bleed silicone oil that can creep anywhere and some are very stable. There are some thermally conductive soft silicones that bleed silicone oil when compressed too much or in contact with porous materials.

  28. #28
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    Default Re: Why no Silicone???

    If you have never seen it, paint that fisheyes is actually rather amazing (in a horribly frustrating sort of way). You just keep painting over a spot with what would seem to be pretty darned sticky paint on any other surface and a couple minutes later, a small round bare spot just opens up - over and over and over. You also want to be very careful about the use of any of those "miracle finish-restoring boat and auto polishes". The type of thing you might see on an infomercial, or something that might be applied to a used boat, to spiff it up right before the owner lists it for sale. A friend once bought a used 22' glass cruising boat that had been painted bright yellow with a brush by a guy who was legally blind. It was seriously ugly, so we ground off the paint and well down into the gel coat with the big disk grinder. Even so, at some point somebody had used one of these polishes on it and the entire topsides fisheyed like crazy when we sprayed it.

  29. #29
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    Default Re: Why no Silicone???

    Quote Originally Posted by Todd Bradshaw View Post
    ...Even so, at some point somebody had used one of these polishes on it and the entire topsides fisheyed like crazy when we sprayed it.
    That should make it a good fishing boat, no?
    "If it ain't broke, you're not trying." - Red Green

  30. #30
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    Default Re: Why no Silicone???

    Yep, they see those eyes and it attracts them. Kind of like the way the sparkles work on a bass boat (even better with the 200 horse Merc on the back to keep up with them when they run).

  31. #31
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    Default Re: Why no Silicone???

    That explains the metalflake! Here I always thought it was because it looks so fantastic...
    "If it ain't broke, you're not trying." - Red Green

  32. #32
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    Default Re: Why no Silicone???

    Outdoor-rated caulking compounds are sold at HD now that advertise 25-year working life.

    Use those, not silicone. It's just a crappy glue.

  33. #33
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    Default Re: Why no Silicone???

    Along with the paint issues, "Silicone" sealant/adhesive has been noted to promote corrosion in metals.
    This is type specific, but I just stay away from it.

  34. #34
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    Default Re: Why no Silicone???

    I read a similar post three years ago. I was so worried about silicone that I threw away a can of it (used for wetsuits) and the box it was stored in before I even started building our dinghy.

  35. #35
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    Default Re: Why no Silicone???

    By the way, after getting tired of the limited lifespan of typical hardware store calk and silicone around the house, I calked a new shower stall a few years ago with 3M 4000 polyether calk that I picked up at Waste Marine. It was indeed more expensive, but I am amazed at how well it has held up and it's still going strong. No more cheap tub and tile calk around here.

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