Re: [ATM] RE: RTV Silicone question

[Mark Holm <mdholm@telerama.com>]

>some new fangled RTV glue at the time (called Silicone II 
>perhaps) which didn't have that classic strong Ammonia smell when it was 
>wet

I think the smell you are referring to is actually acetic acid (vinegar).  At least, every time I have used silicone caulk, the smell I have encountered was definitely acetic acid.

I have seen "silicone" caulk for sale in hardware stores that is actually acrylic latex with only a small percentage of silicone included.  I don't think the Silicone II brand is necessarily bad.  When I saw the stuff that was mostly acrylic, I could tell it was just by reading the fine print on the tube.  Also, silicone is inherently more expensive than acrylic.  I think, but am not certain, that it is difficult, perhaps impossible, to make a good, clear caulk or adhesive by mixing acrylic with silicone, so it may be helpful to only buy clear.  Also, even in true silicone, that pigment probably hurts adhesion a little, so clear is probably still best.

Several times, someone has mentioned on this list a particular specialty grade of silicone adhesive the is recommended for mirror gluing.  I think it is a Dow Corning number grade.  I forget the number but recall, I think, that it is a four digit number.  As I recall, one can mail order the stuff from one of the big industrial supply houses for a not terribly outrageous price.

As I recall, this "extra good" stuff is said not to smell of acetic acid either, because it uses a different curing chemistry, nethanol instead of acetic acid.

Try searching the archive on "Dow Corning".

Mark Holm


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