The Jalopy Journal
Discussion in 'The Hokey Ass Message Board' started by panhead1961, Jan 22, 2013.
What do you use to set flat glass with no rubber gasket? Silicone or urethane?
I went to Napa and bought a Urethane glue by 3m that is made for glass.
Are you talking about setting the side glass in the channels? Urethane
We used to use a butyl rope to set those, I think that they are using Urethane now. Go to a auto glass store/shop, they will probably sell you a tube of Urethane. If you can't find it anywhere else, these guys should be able to help you:
3M WindoWeld Super Fast Urethane, 08609
GET IT AT AUTOZONE ETC.
Silicone has an acid that attacks metal
Urethane is what the car manufacturers use, silicone breaks down with the sun's UV rays..
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
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.
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
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.
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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