On Wed, 30 Sep 2009 16:35:18 +1000, Bob Larter
wrote:

Well, it hasn't happened to me yet, but then the parts I have in foam
have only been there for a maximum of about 3 years.

3 years and a dry storage area is not going to cause problems. Add a
roof leak in my storage closet, and it probably won't last a few
months.

I wonder if it's a
general problem, or whether it's only a problem for particular brands of
foam?

The crumbling to dust problem certainly varies with type and
manufactory. I have some that are at least 30 years old and are in
perfect condition. Others have crumbled to dust. As near as I can
tell, the stuff that is fairly brittle and breaks when you bend it has
survived. The stuff that is fairly flexible, and bends easily, has
crumbled.

As for moisture abosorption, I'll guess(tm) that there some kind of
chemical reaction between the graphite impregnated foam and the
condensed water. It must be something rather strong because, as is
evident in my photo at:
http://www.11junk.com/pics/drivel/slides/black-foam-rust.html
it even corroded gold plated IC leads. I have a difficult time
imagining foam and water creating any acid that strong, but it's
possible.



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# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
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