[pure-silver] Re: a recent problem with fine dust on negs
- From: Jean-David Beyer <jeandavid8@xxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Thu, 30 Jul 2009 06:08:39 -0400
Kurt J. Griffin wrote (in part):
Since it's quiet around here, I'll add my new thoughts. I had a similar
problem last summer that has kept me puzzled, but which I now think I
finally have figured out. I had larger spots (dark on neg, light on
print) when I developed some 120 BxW:
http://www.flickr.com/photos/kjgriffin/2630065990/in/photostream/
Despite this group's suggestions, I couldn't figure it out. It wasn't
until I saw the comment that it had affected only your greys, not extreme
blacks or whites that I went back to my rolls & saw that the same is true
with my shots.
As I was washing film the other day, I realized just how many bubbles
were in the water once I started drawing "cold" water that was in pipes
outside the house at 36 C. I think my usual developing doesn't get the
hotter water until near the end of the wash. When I looked at my records
for the spotty film, it was a rare 2nd round of developing right after
the first batch (which was fine). So, my new hypothesis is that the tap
water I was using for a stop bath (to avoid potential pinholes) had
bubbles coming out of solution and creating small areas where the
developer was able to continue to act longer, producing the darker spots
on the neg. The same must also have been happening on the toe/shoulder
of the curve, but the curves are likely shallow enough not to show up in
the print. That's my crackpot theory. Feel free to laugh until I can do
the prospective experiment.
I have never had this problem, but I was trying to understand it as well (so
I could take preventive measures). Your "cold" water gets even higher than
mine in the summer (here in New Jersey); mine sometimes gets up to about
27C. Now this is not a problem for me in developing, because I do my film in
a Jobo CPE-2, with my (B&W) processing calibrated at 75F. When it gets over
that, I put a block of that blue artificial ice in the water bath until it
gets a bit below that, and all my chemicals are in the bath. So the only
problem would be in my final wash. Since I use TMax films, they are hardened
in manufacture, so they should be able to take that temperature, and I use
F-6 fixer with about 1/2 the specified amount of alum in it, so I get some
hardening. I run quite a high flow rate when washing film, about 1/2 gallon
a minute, and the "washing tank" is the same drum I processed the film in.
The flow rate is so high I would not see the bubbles, if any have time to form.
The situation is different for washing prints. I get the bubbles in winter,
not in summer. I have a Lawler pressure-balancing and temperature balancing
valve set to 75F. In winter, the cold water is considerably under 75F, so
the dissolved gases in the cold water come out of solution when it is mixed
with hot water (varies up to about 120F, depending on the flow from my hot
water heater that is around 40' away). And since the flow rate is still
about 1/2 gallon a minute, but for a Zone VI print washer that takes about a
dozen 11x14" prints, the flow rate (in terms of changes per minute) is very
much less. So it is easy to see the bubbles coming out of solution, and they
form in two places:
1.) in the plenum at the right of the tank (as I face it) just before it
enters the large part of the tank where the prints are, and worse,
2.) on the prints.
I have put a bubbler in the water supply (after the hot and cold are mixed).
This is an air pump designed for fish tank. I thought the dissolved air
would form on the bubbles introduced into the tempered water so that all the
dissolved air would come out in that plenum. Well it helps a little, but I
must also lift the prints out of the washer quickly and drop them back in
quickly so they come off the prints as I wash them.
I asked Fred Picker about this and he said I did not have to do this because
the bubbles would slowly roll off the prints so that no one spot would be
"protected" from washing for very long. Well I studied this by picking a few
bubbles and watching them. I never saw one actually "roll off." So maybe
that worked for him, but it did not work for me.
Now I do not understand why bubbles in the washing process would cause the
troubles seen in your print. I would expect that most likely in the stop
bath, but if you do thinks as I do, those bubbles would have come out of
solution soon after you mixed it up, and before you started processing. I
mix up most solutions at least a day in advance (except amidol developers
that I sometimes use on paper). I put those all in the water jacket of the
Jobo (for film) or in the trays in my sink the first thing when I get ready
to process. So by the time I have the film loaded into the drum, or the cold
light head up to temperature, those chemicals are at the right temperature.
And if they are not, I wait until they are.
--
.~. Jean-David Beyer Registered Linux User 85642.
/V\ PGP-Key: 9A2FC99A Registered Machine 241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
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