Paul Verizzo's None Faster Fixer
This ratio is the "sweet spot" for AT. See my fixer experiments PDF posted here: http://www.apug.org/forums/attachmen...1&d=1207963964
It will clear conventional films in 8 seconds or less and T-Max in 30 or less. Multiply by three for a proper fixing time. Yes, 24 seconds!
Test your own film, your mileage may vary.
The Superfix of mine posted by another APUG member is faster.
Surely no intention to get into a pissing contest, but my tests didn't indicate that.
Originally Posted by Photo Engineer
Lets start at the beginning.
Diffusion controls the initial reaction rate of this material and therefore it will vary from film to film, but basically the accepted wisdom is that it takes 15" to fully diffuse a chemical into a dry sheet of film. (I know, you use wet film in processing, but bear with me.)
So, fixing at the bottom of the film takes 15" on dry film to begin and completion is at about 30". Therefore, fix time is 1 minute for a rough estimate.
This time can actually slow down depending on the developer used and the stop/rinse used before this fixer.
Therefore, you have to consider not just one sheet but what happens over 10 sheets or 20 sheets, closing in on the capacity of the fixer.
If it stays constant, then I would agree with you, but if it goes down, then you have a design problem.
Basically, the fixer you have there is based on the graph in Mees and James showing the sweet spot, but for various reasons we found otherwise due to synergistic effects.
Now, to go further, how did you prove your contention? Did you run retained silver tests? How about wash? Was it faster or slower, and how did you prove the value?
These are questions that should be answered to justify the fact that this is better.
AAMOF, the superfix that was published was #1 or 2 in a series, and I am now up to VII trying to tweak it into shape. I have VIIa on the shelf right now.
So, yes, your fixer works, but it may not be the best for wash rate and the silver retention is unproved.
It may turn out great, but I'm sure that one can be made that is better in several ways.
And, no offence is intended. You seem hyper sensitive to pissing contests, but so am I having had a number directed my way, but I must add that I spent over 5 years of my life at EK working on Fixes and Blixes and have the patents to prove it.
Nah, I'm not sensitive. And I have a hell of a lot of appreciation for the wisdom and experience you impart here, PE.
I think you'll recall my simple experiment seeking only clearing times. My formula is very similar to Formulary F-3, IIRC. So it should be similar in most regards. As to retained silver, haven't a clue. Beyond my scope of ability or effort.
I don't own a copy of Meese, so his work was unknown to me.
At the least, my formula is very simple and very fast.
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I'll agree that it is simple and fast, and I believe that it would probably pass all of the other tests, but as for being the "fastest", that remains to be seen.
That's a duel at sunrise!
Originally Posted by Photo Engineer
Seriously, here's my first bullet. Snipped from my tests and narrative posted:
"2. TF-3 and Superfix both start with a 20% ammonium thiosulphate working strength. That seems pretty typical ammonium thiosulfate working strength over a number of formulas. Time to clear, 16 seconds. pH 7. See Experiment #9 and the note. I came back to this, thinking that something was amiss. Sure enough, with film fresh out of the bulk loader plus some 3-8 minutes in water, the times changed to 8 and 9 seconds with two trials.
(First and very important observation: Testing by time to clear has variables. The time the film was left in the light and the light intensity seems to be very critical. Perhaps the water soak, too. “Develop” your own procedure and stick to it. You can use dry film for your own fixer life span checks. I even had film clear after a day left soaking in plain water that had previously soaked film in it. Might be the iodide dissolved out, it is a silver reducer.)
3. I then added 10 g each thiourea and ammonium thiocyanate to get the core Superfix. Surprise! Time to clear, 20 seconds! I added 10 more grams of each, and the time went up to 27 seconds! This is exactly the opposite of all expectations. I’m willing to admit that this could be procedural fault on my end. Since this formula wasn’t my prime interest, I went on. pH: 8+, just as Ron says without the acetic acid. See #2 and my revisit.
Revisited: With the carefully weighed thiourea and ammonium cyanate, and “fresh” film from the bulk loader two times, my new times were 10 and 9 seconds. I then added 5ml of a 14% total solution of thiourea and ammonium cyanate and got 12 and 10 seconds. I added 10ml of the above and the times increased to 12 and 11 seconds."
In brief, despite all expectations - yours and mine! - adding urea and thiocyanate slowed the reaction time. I can't explain it, but there it is.
Also as I pointed out elsewhere, whether the film is dry or wet is a huge variable, something that threw off Kodak researchers into the 1930's; inconsistent results. As I discovered, it also matters A) how fresh the film is from the bulk loader, and B) how long it has been soaking.
So, yes, many variables, but once I learned them, I tried to be consistent.
As I could process a film in 2.5 seconds that's developed & fixed isn't this just a little bit slow
To start with, 250 ml of 60% Ammonium Hypo solution is 150 g/l. I use 200 ml of Ammonium Thiosfulfate which is 120 g/l, and not the 20% you quote. So, I use less hypo.
Both are within the sweet spot that both Mees and Haist disclose. What they don't say, and what you have missed is that dry experiments don't agree with wet experiments but are reproducable. Wet experiments differ from dry, but vary according to developer and the treatment after the developer. So, both ways have faults. I am aware of this and I have alluded to it in my first post here. I used the dry method to formulate many Kodak bleaches, fixes and blixes and the fundamental lab work for the blix patent was done on dry strips for the sake of uniformity.
That said, lets take an example of a fix that works in 1/2 minute but requires 4 1/2 minutes to wash and another fix that works in 1 minute and washes in 1 minute. Which is the better fix? Which is the faster?
Ian is totally correct. If he can process film in 2.5 seconds then your results and mine are moot!
Now, as for some other details. The pH of a fix wrt to its formula is very important. TF-4 at pH 6 would be a different beast, and any of my super fix formulas at pH 7 is not the original at 6.5. And, urea is not thiourea. Also, urea can either accelerate or retard fixing depending on pH and thiourea alone is a slow fixing agent that also varies in fix rate as a function of pH. It is also a carcinogen.
So, the total process time, as Ian has shown us is critical as is temperature. In my second post here, I alluded to some of this by asking what the silver and hypo retention factors were at the end of your process. High levels of hypo are notorious for being difficult to wash out, and are notorious for leaving behind some silver complexes. I'm not suggesting this is the case, but I am suggesting that you test for this.
I am seeking the proper testing of your fix formula and nothing more. Yes, you see clear film. I can with a fix formula as well, but I get reticulated film from one formula and retained silver from another. All of my formulas are tested for fix rate, wash rate, and senstivity to process. The criteria are retained silver and retained hypo which relate to image stability.