dancqu
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Well Now! An opportunity for Mr. Troop to toot HIS
own horn for a change. Perhaps a list of Journals of
this and that Society in which his findings have been
published.
For myself I tire of the endless applauding and leaning
upon of such as Levinson and Haist who finished their
work 40 and even 50 years ago. Dan
PS: Levinson or Levenson? Depends upon whom you
are reading, Ron or Bill.
the book I originally wrote was about five times longer (no exaggeration) and would have been unpublishable in the late 90s. My question is, what is publishable today?
I would also point out that I have almost always said that (like others) I find it almost impossible to believe that the Ilford sequence works, and that (like others) I normally repeat one step, or let it sit for a little while in the distilled water after the triple set of inversions.
I am an engineer by nature, which only means that when I have an engineering problem before me, I read books and write equations and do whatever else is necessary to find a solution. I had occasion while employed by NASA to solve problems in aerodynamics, electronics, photography, human factors and some I don't remember.
Hydroquinone Clearing Agent. How about THCA? Bill
mentioned the subject years ago on rec.photo.darkroom
and still no THCA.
"Just as a caution, one popular fixer out there is so poor that,
it spoiled on my shelf before I could get to test it, so beware..."
Likely one of those "rapid" ammonium fixers. I've got some of
that to dump as well. What remains of my bottle of anhydrous
sodium is in fine condition several years after being brought into
stock. If one is an off, off, and on such as myself at work in the
darkroom, a dry easy to mix concentrate is the ticket. Spoon
up fresh fix each turn in the lab. Dan
This is true only for the diffusion part. The Donan membrane property applies to gelatin coatings, but there is also ADDITIONAL problem of adsorption of thiosulfate to gelatin as well as silver image. The latter is much slower process with greater time constant. It's just that in the case of film and RC washing the relative importance of the desorption process is much smaller than baryta paper.The driving force for removal of substance x from the emulsion is proportional to the difference between the concentration in the emulsion and the concentration in the wash water, I would expect.
In practical terms, you'll need more agitation and longer time in later cycles.A problem here is that the driving force is also less at the beginning of each cycle than at the beginning of the previous cycle.
I use current ISO standard for "other fine grain films" although I give a generous safety factor.I haven't read this thread as thoroughly as I should have, but I do not recall that a target value for residual x has been set.
In my previous life I was an engineer as well, and I know what you mean. Now I'm in science world, and the word "engineer" is often used in derogatory way. I usually don't like to hear that. But maybe not today. Some "engineers" and others on APUG seems to do the exact opposite from what you said. They get bored sitting around computer all day, pick a dead issue to tackle with and reverse engineer the existing solutions by reading books, writing equations, and do whatever else is necessary to find something to talk about endlessly.
Also, if all my negatives tested negative of residual thiosulfate every time I tested the Ilford method with 99% of my luck, I think everyone has the 99+ per cent of the luck. I occasionally win grand prize on fine art juried competition, but I never win lottery tickets and I don't even bother to buy one.
The best thing to do, probably, is to ignore threads that are trashed by some people you see...A very interesting thread, but what are we, as practical photographers, to do with it?
Developer retention is not an issue if you follow any of the archival washing sequence. Practically speaking, it is a problem only in monobath system. Don't worry.What I take away are a couple of things - one, since I don't use an acid stop bath, perhaps I should extend the time the negative spends in the water between developer and fix to better remove developing agents. I now go 30-seconds with agitation.
Two, I use an alkaline fix (TF-2) with non-T grain films. Keep better track of the number of negatives put through it to be sure the fixer is fresh, and wash using something like the Ilford method but allow the negatives to soak for five minutes between washes.
Sometimes things seem to work. The real test will come only after years of keeping. If you don't believe me, read the seminal work by Ctein who sold prints he thought were archival even after tests. After customers began complaining about a batch of prints, he ran additional tests under different conditions and discovered his prints were not archivally prepared. He makes his living by selling photographs and writing about photography. His reputation was at stake here. He fixed the problem, replaced the prints and wrote about his experience. BTW. He over washed. So, there is a sweet spot that the experts have found for us. We should listen to them.
Do what you wish. Remember that even a figure like Ctein was blindsided.
PE
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