4 Dec
2016
4 Dec
'16
3:24 a.m.
On Sat, 3 Dec 2016, drlegendre . wrote:
Interesting find, thanks for posting this. I've
seen this as well. with a
batch of old ICs which had been stored (in black foam) for some 20-30
years. The leads kind of just stayed behind in the foam..
My assumption was that the foam was simply hygroscopic, and held enough
atmospheric moisture & pollutants to foster corrosion.
There are numerous black foam formulations.
I inherited some lenses (including a Leitz Tele-Elmarit 180mm (<250 made))
that had been stored for a few decades in an essentially airtight case
with black foam. When I first opened the case, it seemed as though there
was liquid in the case, with an intense vinegar? smell. Second time that
I opened the case, a few hours later, it was dry and crumbly, and the
outer painted surfaces of the lenses were badly pitted and had to scrape
bits of the foam off, but NOT at all like water damage. It turned that
lens from mint condition and a major rarity, into usable but POOR cosmetic
condition (a loss of more than a thousand dollars in value!).
(Three other cases had simply disappeared between the time my buddy died
and the time that the county let us go through the house.)