By the way, what's the latest formula for your SuperFix, PE (if you're releasing it)? In the articles section I could find the formula, and there you mention you were up to version VII to be released shortly, circa 2006.
I had one criteria, I tried to be consistent and careful. I wasn't studying wash rates, rinse or stop, or diffusion rates. Just how fast fixer A was compare to B compared to C, etc.
Originally Posted by Photo Engineer
Despite my many, many hours of reading texts, I've never come across an experiment like this.
I once used a darkroom that was stocked with Kodak X-Ray fixer. This is a concentrated ammonium thiosulfate acid fixer with hardener that is normally used in X-O-Mat processors, but it can be diluted properly and used in trays. I found it was extremely fast and powerful. In fact, you had to be careful because it bleached prints (on Medalist) noticeably in as little as 5 or 6 minutes.
I looked at a lot of x-ray fixers, either msds or patents. Most were just concentrated versions of ammonium thiosulphate, some also used the sodium. The Panadent caught my eye because of the lack of thiosulphate and using ammonium thiocyanate instead. Wouldn't it be nice to not have to rinse out thiosulphate? An expensive chemical, BTW, compared to the other typical ones. But my experiments showed it to be a dud.
Originally Posted by nworth
I really, really think that a number of MSDS's are misleading, whether intentionally or just carelessness. I know that some of the patents I looked at were sort of bizarre in one way or the other.
Someday I'll get curious again and revisit that.
Thanks Paul, for a very interesting and useful piece of work!
Everything is analog - even digital :D
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Originally Posted by David A. Goldfarb
I'm testing prototype mixes, as the formula had to be changed slightly for production reasons. I would have to let Bud give the date though, because even if I had finished all the tests, the release would be up to him.
As for Paul's work, it is excellent, and I apologize for both seeming negative and not congratulating him on it. I've run this type of test before, but never published it. I used this type of test to develop the EP3 blix and the super fix. to name two. I also used it to develop our patented film blix.
In any event, the only thing I questioned reall was his definition of fixing time and his observation of the short times for fixing.
Good work Paul.
Too much on which to comment.
I'll clarify one matter; Film vs Paper strength.
Working strength fixers have two limits of capacity.
The first limit is simply the chemistries capacity for silver.
The second is the safe limit for silver levels in the fixer.
In a nut shell film strength fixer has a chemical capacity
way beyond it's volumetric silver capacity when used as
a paper fixer. That is, to remain within an established
silver level when processing paper using film strength
calls for dumping considerable good chemistry down
Check Ilford's fixer PDFs. You'll find that on a chemical
capacity basis a dilution of 1:19 will exhaust the chemistry's
capacity while remaining within the fixer's volumetric silver
levels. The "sweet spot". Averaging included. Dan
Just a few comments then. Fixing is not equal to clearing. Fix time is 2x the time to clear because clearing can take place, but the silver complex must begin to leave the coating for fixing to be effective. If TF-3, 4 or SuperFix are not at their optimum pH values, they won't fix properly, and finally the "sweet spot" I refer to in Mees and James is the optimum concentration for the most rapid fixation rate. It is a "U" shaped curve where the rate is slower on each side, namely low and high concentration. This curve is what you observed when your fixing was slow at high concentration and sped up as you diluted the fix. It then slowed down as you diluted things too much.
Yes, I know. But without extensive other stuff, visual clearing was the standard. And regardless of safety margins or other matters, all the fixers and variations were held at a constant. I was interested in one possibility compared to another, not the absolute correct answer. I think that my speed conclusions are the core results and that it would be difficult to change the ratings much by pH or other variables.
Originally Posted by Photo Engineer
The U-shaped curve is also in Haist, so that was my source of knowledge on that matter.
I appreciate your return and thanking me for my work. I was taken a bit aback on your first comments.
Of course, I wasn't addressing this at all........
Originally Posted by dancqu
(And my next line of thinking is why not put some steel wool in the stored fixer for the silver to latch onto? Probably too simple.)