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Old 10-16-2016, 02:12 PM   #1
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Silicone removal

Our recent move of HEY JUDE to the coast necessitated removing the pilot house roof, glass & windshield frame exposing damaged gelcoat under the frame, ~ 8' x 2". I'm guessing earlier in her life the frame was sealed with something like 5200 & when the roof was removed in 2003 for transport from FL to TX the damage occurred. When re-installed in 2003 a silicone caulk was used to bed & seal thus the frame separated from the base fairly easily. When re-assembling I will bedded with butyl tape & seal the edges with appropriate caulking.

My question is... after I scrape & sand off all the old silicone possible, what are your recommendations to remove the very last bits of silicone prior to my gelcoat repair?

Thx, PD
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Old 10-16-2016, 03:00 PM   #2
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Plastic razor blades, your finger nails, etc.
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Old 10-16-2016, 03:03 PM   #3
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If you're really removing more material from both faying/meeting surfaces after you've already removed all sign of the previous goos, then I think you're home free.

Most folks who suffer from silicon-itis are striving to not damage/alter/remove the original/shiny/unblemished materials.
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Old 10-16-2016, 03:05 PM   #4
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PD,
Glad you asked. I'm faced w the same problem on a small boat I just bought. Some caulking of wood trim on the transom was done w silicone. I hear the usage of silicone caulk will make adhesion of other caulks very poor. I'll probably be using Sika-Flex and I'm very interested in good adhesion.
Thanks for the post.
Silicone does have great adhesion to glass, aluminum and other hard surfaces. There are many different kinds of silicone and it's possible silicone could be good for your application.

Bill and DH,
Isn't there a good solvent for removing silicone residue from surfaces where it has been?
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Old 10-16-2016, 03:15 PM   #5
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Greetings,
Mr. HJ. Ah, the dreaded (by me, at least) silicone. I promise, no rant, THIS TIME!
In a previous life where I developed my, ahem...true feelings about silicone, the solvent of choice was Xylene or Toluene. Both should be available at a big box hardware store and might be sold as Xylol or Toluol (sp?).
I would use one of these as a wipe-down after removing as much trace (ala Mr. 11's suggestion) material as possible. Lots of paper towels changing to a fresh sheet often.
Two things to consider. Your sandpaper/paper towels/rags/gloves will be contaminated with trace silicone so discard everything after use AND most importantly, BOTH solvents are very bad health-wise so hand and lung protection is very important. Do NOT leave solvent contaminated material anywhere around the boat. Spontaneous combustion is a good possibility.
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Old 10-16-2016, 03:35 PM   #6
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Quote:
Originally Posted by Nomad Willy View Post

Bill and DH,
Isn't there a good solvent for removing silicone residue from surfaces where it has been?
https://www.dowcorning.com/content/p...it/26-1880.pdf
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Old 10-16-2016, 03:44 PM   #7
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I've used MEK (Methyl Ethyl Ketone) to remove silicone. As with may strong solvents, it ain't good for you so some strong gloves and a fan or breeze to blow away the fumes.


Wet a part of a rag with it and the silicone comes right off with just a bit of rubbing.
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Old 10-16-2016, 06:10 PM   #8
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Indeed there are sealant removers advertised and available. My research a number of years ago involved going right to Dow Corning or GE (don't remember who) and asking. I was told that the silicone cannot be reliably removed from window glass, but that grinding the fiberglass would get rid of it on that side.

Various aggressive solvents make a good start. My solvent of choice is lacquer thinner. Tough on hands, acrylics, plastics and latex paint. OK on oil paints, polyester and epoxy.

I don't think that most solvents are likely to cause spontaneous combustion. The classic oily rags in a bucket spontaneously combusting is stuff like linseed oil. It's polymerizing and giving off heat, not evaporating. Of course, you could be solving linseed oils which would still be dangerous. But who wants to smell any of these things? I always hang solventy paper towels or rags outdoors over something that won't burn; hung so that any heat dissipates and the solvent dries quickly.
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Old 10-16-2016, 06:43 PM   #9
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I`ve not tried it, but a final clean with a fine rotary Dremel brush wheel might work.
There are 2 kinds of silicone sealant here: Bathroom - not paintable, Roof & Gutter - paintable. Hard to tell what was used unless you know. Your products may vary.
I`m a fan of Sika, and other brands of polyurethane sealant/adhesive. I used a competing brand to glue teak mounts on the FB for my solar panels, still stuck hard 6 years on.
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Old 10-17-2016, 12:22 AM   #10
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I've used Xylene and I know a fiberglass repair person who uses Xylene. He hates silicone with a passion.

As pointed out is a a nasty chemical, Xylene, so use high quality rubber gloves, a good breathing mask with chemical absorbing filter change each day at least, even using a fan behind you to blow fumes away as much as possible.
It may also require some mechanical abrasion. I have also use a mini ss wire brush to remove the gel coat. They are small enough that with some care and some taping they will remove the area wanted without wrecking adjacent areas.
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Old 11-01-2016, 01:40 AM   #11
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Thx all for your suggestions. I was able to find the Dow chemical only in 45lb bucket thus I did not try. What did work was a combination of a 1" sharp scraper, a 1/4" wood chisel, a 1"x 2" stiff stainless steel brush (HD) & a course dry rag. I'll sand everything well before applying new gelcoat using a 1" foam brush.
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