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[Mogrits <mogrits AT gmail.com>]

On Sun, Mar 8, 2009 at 1:42 PM, Gene GeRue <genegerue AT ruralize.com> wrote:
> Warren, please educate me on why silicone caulk would be bad for
> sealing metal roof nail holes.

Because silicone breaks down in sunlight. Additionally, it loses
adhesion to metal over time. Even the "UV resistant" silicones seem to
shrink with age and eventually pull away. If you've ever noticed,
silicone caulk seems to get "greasy" as it cures. It's my belief that
this off-gassing is what breaks the bond to metal.

Metal building manufacturers don't ship their buildings with silicone
caulk- they all have a proprietary brand of urethane sealants which
are similar to the NP-1 I first mentioned.

But the simplest solution to the problem mentioned in the original
post is still "Peel & Seal".

Warren