Mega Fixer Tests

[Paul Verizzo]

I've done a lot of research and a number of tests of fixer formulas and their speeds in the last week. This includes sodium and ammonium thiosulfate based, thiourea and ammonium cyanate, various concentrations and additives.

The results might surprise you.

PM for a copy in PDF. Or, paulv (AT) paulv.net .

 

[Bruce Osgood]

Why can't you just put it up here or in the Articles section?

 

[Paul Verizzo]

Simple.

Why can't you just put it up here or in the Articles section?

I couldn't see how to do it! Nothing there for new posts, just something about things being reloaded....for days.

 

[Paul Verizzo]

Don't forget your email address.

I've done a lot of research and a number of tests of fixer formulas and their speeds in the last week. This includes sodium and ammonium thiosulfate based, thiourea and ammonium cyanate, various concentrations and additives.

The results might surprise you.

PM for a copy in PDF. Or, paulv (AT) paulv.net .

Don't forget your email address.

 

[David A. Goldfarb]

You can attach a PDF to a post, just like you would attach an image, but the file size limit might be on the small side, so if you have it in DOC format, that's another option. Click on "Post Reply" and then "Manage Attachments" to upload the file.

 

[Paul Verizzo]

You can attach a PDF to a post, just like you would attach an image, but the file size limit might be on the small side, so if you have it in DOC format, that's another option. Click on "Post Reply" and then "Manage Attachments" to upload the file.

Thanks, I'll do that later today.

 

[Paul Verizzo]

OK, here it is as an attachment

I hope I did this right......

 

[David A. Goldfarb]

Came up fine here. Thanks for the report.

 

[Paul Verizzo]

Came up fine here. Thanks for the report.

Thanks for the help! I'm still pretty new on the system here.

 

[Photo Engineer]

Well, what is your definition of fixing time? Is it 2x the time to clear? Or what?

Also, there is a sweet spot as shown in Mees, and Mees and James.

If SuperFix and TF-3 or 4 have the same pH, something is wrong. SuperFix should be about 6.3-6.7 and TF3 and 4 should be around 7.5 - 8 or somethng like that.

Wet and dry is important, but the results are consisant within a test depending on how you do it and how you measure rates. You have to look at the back of the film. Also, wash rate is important and is determined by the fixer, and fix rate is often determined by the preceding bath (rinse or stop)

BTW, due to the average thickness of film, dry film requires about 15" for fixer to diffuse to the bottom.

Oh well, I've been doing this for years now.

PE

 

[David A. Goldfarb]

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.

 

[Paul Verizzo]

Well, what is your definition of fixing time? Is it 2x the time to clear? Or what? As said, time to clear.

Also, there is a sweet spot as shown in Mees, and Mees and James. Sorry, I don't own Meese, might have read stuff at the Cal State library 20 years ago, but I don't recall. If so, I apparently didn't xerox anything on fixers.

If SuperFix and TF-3 or 4 have the same pH, something is wrong. SuperFix should be about 6.3-6.7 and TF3 and 4 should be around 7.5 - 8 or somethng like that. As said, no acids, alkalis, alums, etc. were used.

Wet and dry is important, but the results are consisant within a test depending on how you do it and how you measure rates. You have to look at the back of the film. I just watched the film clear as I swished it around. Sometimes it took a moment to decide if it was clear or had a bit of spot still. Human subjectivity. Also, wash rate is important and is determined by the fixer, and fix rate is often determined by the preceding bath (rinse or stop)

BTW, due to the average thickness of film, dry film requires about 15" for fixer to diffuse to the bottom.

Oh well, I've been doing this for years now.

PE

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.

Despite my many, many hours of reading texts, I've never come across an experiment like this.

 

[nworth]

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.

 

[Paul Verizzo]

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.

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.

 

[Tom Hoskinson]

Thanks Paul, for a very interesting and useful piece of work!

Cheers!

Tom

 

[Photo Engineer]

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.

David;

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.

PE

 

[dancqu]

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
the drain.

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

 

[Photo Engineer]

Paul;

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.

PE

 

[Paul Verizzo]

Paul;

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.

PE

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.

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.

 

[Paul Verizzo]

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
the drain.

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

Of course, I wasn't addressing this at all........

(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.)

 

[Photo Engineer]

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.

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.

Paul;

The comment about fix vs fix time was intended for those who don't know the difference. That was not a criticism, but it did explain why my numers, should I publish them would be different than yours and so would some others.

I think it is a fine test. Keep it up.

PE

 

[dancqu]

Of course, I wasn't addressing this at all........

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.)

Not too simple. Very likely disastrously contaminating;
the silver comes out of solution and iron enters solution.

As for Film strength vs Paper strength, the subject
was broached in the PDF as a question. Three frivolous
reasons were given for there being two strengths. My
previous post gave a least one GOOD reason for the
two strengths and even a third strength. Paper
strength, 1:7 or 1:9 may be an industry
compromise. Dan

AFAIK, Film strength for Paper was an Ilford invention.
At the very least it was popularized by them as part
of their Archival Processing Sequence; no longer
mentioned. I've not found any reference by
Kodak suggesting a 1:3 or 1:4 film
strength for paper. Dan

 

[Photo Engineer]

It may be worth noting that according to some sources hypo and silver hypo complexes tend to bind to baryta. This is reported in the literature somewhere, but I have forgotten where I've read it.

I have found that my coatings on plain papers of the same weight as the baryta I coat on seem to wash faster. If this is all true, then it might not be a wise thing to use a concentrated fix for FB papers. Just a thought.

PE

 

[Paul Verizzo]

Pondering...

Paul;

The comment about fix vs fix time was intended for those who don't know the difference. That was not a criticism, but it did explain why my numers, should I publish them would be different than yours and so would some others.

I think it is a fine test. Keep it up.

PE

Yes, I should have used the phrase, "Time to Clear", instead of "Time to Fix."

Too late for the copies that have gone out there, but I will change that when I have time.

So, thanks for the constructive critique.

 

[Absinthe]

Paul --

Just an observation, perhaps something to consider. If the ph is truely a concern, have you accounted for the fact that in most cases, (at least as far as I remember) one is going directly from the stop bath into the fixer. It would aoppear at least in my mind, that one would be dragging a fair amount of stopbath into the fixer, would that not lower the ph significantly?