Re: [APML] TP woes - the verdict

[Robert Reeves <reeves10@swbell.net>]

> What exactly do you mean by 'exposed to humidity'.
> I ask this because...yes it gets humid around here.

Then you are in Tech Pan trouble.  I'll second Kent's comment about how
critical it is to keep hypered Tech Pan as dry as possible.  A half hour
exposure to 60% humidity (or so) at any time in the film's hypered lifetime
is enough to cause noticable problems.

> But how much humidity is too much for tech pan?  Is the
> tp unaffected until dew starts forming?

If dew is forming and the film is exposed to air, your in trouble already.

Or can it fog simply from
> moist air?

Yes, moist air can render a hypered Tech Pan exposure a useless contrastless
blob.

Plus if it was humidity, wouldn't I see all sorts of
> blotching and unevenness in the film base.?

You will, but if the humidity exposure is high enough, the film will fog
over completely.

Every frame I developed
> was relatively consistent.  consistently dark..yes..but very even.
> Also, I developed many unexposed frames that never saw
> any light.  Would humidity affect the unexposed frames wound up
> in the canister?

Not as much.  There should be some difference.  If there is not, then the
problem occured when all the film was removed from the cassette, such as
when it was loaded into the hyper chamber or put in a developing tank.  For
instance, if you load the developing tank in a changing bag and you are hot
and sweaty, the developing tank will have humid air in it.  This will be
fogging the film in the tank while you prepare your developing solutions.

How dark is dark on your Tech Pan?  A rule of thumb I used with my low
vacuum hypered Tech Pan was that the unexposed film that had been kept very
dry had a one f/stop density to it as I measured it with a hand held light
meter.  This was with 11 minutes in D-19.  Not as precise as folks like
Jason Ware or Wallis and Provine, but for what I had on hand, it worked for
me.

Robert Reeves                      reeves10@swbell.net
520 Rittiman Rd.                   www.robertreeves.com
San Antonio, Texas 78209    210-828-9036
USA                                     29.484  98.440  200 meters


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