hr(bob) wrote:

I am installing some thermopane style glass to replace 25 year-old
thermopane glass that had lost itsr seals and become cloudy. The
glass company where I had the windows fabricated gave me a caulking
size tube of Industrial/Construction RTV Silicone - "professional
Quality" manfactured by c.r.laurence to use when mounting the glass
in the window frames. I'm trying to figure out how this silicone
rubber differs from the "standard" silicone rubber sold at hardware
and big box stores.

The glazer uses RTV that doesn't give off acid fumes (vinegar) when it
cures (like the kind you're not supposed to use with cars equipped
with exhaust oxygen sensors) but instead gives off alcohol fumes (like
the kind that's OK for oxygen sensors), and it may be softer. You can
buy special glazing RTV anywhere, and GE and Dap offer it:

http://www.amazon.com/Silicone-Windo.../dp/B000M2UPAG

The description says it's sunlight resistant, but all silicone rubber
naturally is, so maybe glazing RTV is more resistant to turning
yellow, unlike the ordinary clear stuff that had been sealing our
solar collectors for 30 years in the Arizona sun and eventually
developed a slight tint.