Get that F'ing foam out of there!!
Not only does it get crumbly, there is sometimes an intermediate stage
where it smells like vinegar, and is a strong acid.
When my best friend was alive, he stored his camera stuff in airtight
cases in foam.
After his death, I went through what was left of his stuff.
One case had a Visoflex, bellows, and a Leitz Tele-Elmarit 180mm M
Visoflex mount lens. 250 of those were made. One in decent shape goes
for $2K. His was brand-new, quite possibly the last, and only one in
perfect shape. The foam ATE into the barrel of the lens, destroying all
Grumpy Ol' Fred cisin at xenosoft.com