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Silicone or urethane on glass

Discussion in 'The Hokey Ass Message Board' started by panhead1961, Jan 22, 2013.

  1. panhead1961
    Joined: Oct 4, 2012
    Posts: 30


    What do you use to set flat glass with no rubber gasket? Silicone or urethane?
  2. Tin Can
    Joined: Nov 18, 2005
    Posts: 2,098

    Tin Can

    I went to Napa and bought a Urethane glue by 3m that is made for glass.
  3. Are you talking about setting the side glass in the channels? Urethane
  4. TagMan
    Joined: Dec 12, 2002
    Posts: 5,949


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  5. fordcragar
    Joined: Dec 28, 2005
    Posts: 3,180

    from Yakima WA.

    Joined: Feb 9, 2003
    Posts: 682


    3M WindoWeld Super Fast Urethane, 08609


  7. manyolcars
    Joined: Mar 30, 2001
    Posts: 8,063


    Silicone has an acid that attacks metal
  8. inthweedz
    Joined: Mar 29, 2011
    Posts: 356


    Urethane is what the car manufacturers use, silicone breaks down with the sun's UV rays..
  9. acme30
    Joined: Jun 13, 2011
    Posts: 147

    from Australia

    I was told to never use silicone on glass or new electrical parts - story was that over time (at a particle level) the silicone will migrate across the glass or electrical component thus leaving an invisible film that you can't wash or clean off without solvents.

    Someone here will probably say balls to that but there you go:rolleyes:
    Last edited: Jan 23, 2013
  10. txturbo
    Joined: Oct 23, 2009
    Posts: 1,771


    interesting.....circuit boards in newer GM instrument clusters are covered with a layer of silicone to seal out moisture....I have to clean it off to solder connections......also about the urethane.....I wouldn't use it until I talked to a glass place about it. The black stuff they use on modern windshields is UV sensitive...thats the reason for the black band around tha glass. Supposedly it will harden, shrnk and crack when exposed to UV and that leads to leaks. I have a buddy that had a winshield place come and install a new winshield in his 66 mpala and instead of using the original type rope seal he used the black urethane. It has been a bout a year and its hard as a rock and is starting to crack.
  11. tb33anda3rd
    Joined: Oct 8, 2010
    Posts: 15,264

    1. Connecticut HAMB'ers

    never use silicone.
    when setting side glass in the window track. use a small dab of urethane inside the track on either end, put the glass in the channel, then put a small bead across the top of the channel, on both sides of the glass. this will allow the glass to be changed, if need be, by using razor blade to cut the bead off. do the same for vent windows
  12. CutawayAl
    Joined: Aug 3, 2009
    Posts: 2,144

    from MI

    I agree, silicone isn't what you want for this. But just fir general info; there are several kinds of silicone RTV. Only the most common "regular" kind is acid cure.
  13. Ralph
    Joined: Jan 8, 2004
    Posts: 295


    I sold Silicone and Urethane to glass shops for 20 years. Use the urethane. Get the heavy bodied, non sagging stuff. Takes a heavy duty caulking gun to push it. It's not the acetic acid the silicone gives off as it cures that's the problem, there are neutral (alcohol) cure silicones too. The problem is that silicone is "vapor permeable", so water vapor (humidity) goes right through it, and rust starts underneath. Use the urethane, it's NOT vapor permeable, and waaay stronger. Put an edge band of black maybe an inch wide all the way round so the urethane doesn't get sun exposure. There's a special product for that, that bonds well to glass. Not paint. Remember that if you cheap out and use paint for the edge band, now you're bonding to the paint. Paint comes off glass easy.
    Oh, and inthweedz had the right idea, but the products reversed. Silicone isn't affected by UV, but urethane is. That's why txturbo's buddy's urethane is cracking, and why you need the edge band.
    Finally a topic I can give a knowledgeable answer to!

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