Re: Wet HIE Film Boxes

[boblong@xxxxxxxxxxx (Robert Long)]

On Sun, 05 Jan 1997 03:01:36 +0000 (GMT), you wrote:

|it is a verb as well, as in Dutch, otherwise substitute with=20
|sublimation....;-)), in relation with its air content. A film=20

You've taught me the correct use of a word I've been using since I was
a kid.  A teacher said that sublimation meant the direct evaporation
(without intermediate melting) of frozen moisture.  That's the way
I've used the word ever since.  My regular dictionary contains no
definition at all that fits the present context, so I looked in a
scientific dictionary.  Behold, only one definition: to condense from
vapor, as heated iodine on the walls of the vessel.
=20
|I think the main confusion is that I open my containers and *seal*=20
|them again after exposure or non-use (can remember the latter ever=20
|happened though).
|Also note that all the rime in your freezer comes from frequently=20
|opening it up to a fresh supply of relatively humid ambient air.

My point exactly.  When you open the sealed film container, you let in
the ambient atmospheric moisture.  When you reseal it, it's like
closing the freezer door: it traps the moisture inside.  If the
container is then cooled below the dew point of that trapped
atmosphere, condensation *must* result.  Since the inside surface of
the container cools first--that is, before the cassette or the film
inside the cassette--it receives the first moisture.  If you have
never had enough condensation to affect the film, it is just a matter
of luck.  The only way you can be sure the film is safe is to leave
the inner, moisture-proof container (sealed at the factory, one
assumes, in very low ambient humidity) sealed and only refreeze what
is still sealed.

Once you have opened the container, you *might* lower the chances of
damaging the film by leaving the container unsealed in the freezer, so
the trapped moisture can escape--hopefully, before it condenses.  But
I agree with your implied objection that leaving the film cassette in
the freezer without any container probably is worst of all.

The moisture damage on the boxes of the films I store in my freezer
convinces me that I do well to heed the film manufacturers' warnings
to thaw before opening and not return to the freezer a package whose
vapor seal has been broken.

Bob Long
(boblong@xxxxxxxxxxx)

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End of INFRARED-PHOTOGRAPHY Digest 169
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