Thanks for the feedback. I especially appreciate the life estimates.
Chuck Norcutt
Garth Wood wrote:
> Chuck Norcutt wrote:
>> But it it's hermetically sealed why does one ever have to change the
>> dessicant?
>
> Chuck:
>
> As far as I can tell, it's a combination of things:
>
> 1. You do open the cases from time to time, and the dessicant's capacity
> for humidity adsorption isn't unlimited;
>
> 2. There is some humidity clinging (for lack of a better term) to the
> metal and glass (and interior non-sealed air spaces) of the lenses; and
>
> 3. Silica gel dessicant seems to "auto-reverse" its adsorption by
> outgassing every so often.
>
> There's also the issue of adsorption while they're cooling down after an
> oven treatment (so they never go back into your cases "fully-charged,"
> so to speak), and I have no idea of the efficacy or accuracy of the
> indicator dots. I do notice that if I'm in and out of the cases
> relatively frequently, I'll only get a month or so worth of protection
> according to the indicator dot before I have to recharge. If I leave
> 'em alone, they can last many months. They never last forever, though.
>
> I like 'em 'cause they don't require power on a regular basis -- if
> that's never a concern, don't go with that solution.
>
> And as for the quality of the seal on the boxes, as far as I can tell,
> they're watertight. I've dunked 'em as tests, and I can't get 'em to
> leak under a foot of water. I have no idea how well they resist
> pressure differentials of atmosphere.
>
>
> Garth
>
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