> I've taken to putting silica gel packets in some of my
> letterboxes in hopes of keeping water vapor out of the air.

We had considered doing that, but also wondered how much of
a difference it would make. Couldn't hurt, anyway...


> I don't know yet if it helps, but it should. I know the gel
> has a limited useful life, so I intend to replace the packets
> each time I visit a box.

The useful life of silica depends on how much moisture it has
to adsorb, it doesn't actually go "bad", so in an air-tight
box they *should* last almost forever. If even a little bit
of liquid water gets in, though...
Also, you can re-activate silica by scattering it on a cookie
sheet and putting it in your oven for a while. You'll have to
check the brand that you get, but around 200C for an hour or
two works for most (just remember to put them in something
airtight *immediately* after taking it out of the oven).



- Ben of RIBNAG