Acetic acid as stop bath for film?

clayne

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Btw the dye test is only partially accurate. The source of contamination, the film, is what emanates the contaminant into the water. A full dump with dye is different than a full dump with contaminated film.

The 66M L argument is just math games and ignores the fact that in using running water we also remove water as well.
 

Ian Grant

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clayne said:
Btw the dye test is only partially accurate. The source of contamination, the film, is what emanates the contaminant into the water. A full dump with dye is different than a full dump with contaminated film.
Click to expand...

That's true but what is being tested what is a complete change of water, how much does it take & how long rather than Kodak's rather vague statement.

Ian
 

clayne

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Ian Grant said:
That's true but what is being tested what is a complete change of water, how much does it take & how long rather than Kodak's rather vague statement.

Ian
Click to expand...

Probably heavily related to the direction of flow, dynamics and pressure of flow, and exit path.

Tank with a hole in it would probably be ideal. Slow flow into an open top tank might just result in a lot less displacement of old fluid.
 

Ian Grant

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The dedicated film washers were water fed from the bottom edge in such a way that the circulation swirls up from the bottom with a good flow rate, they used far more than the simple complete change of water in 5 minutes that Kodak suggests. Mine came with a job lot of darkroom equipment years ago it's nothing more than a simple tank, ok you can stack more sections for more spirals but it's nothing fancy.

Most of us have our own film wash routines that fall in between both Kodak & Ilford's recommendations, and are fine in terms of archival permanence. It's the rather vague Kodak recommendation that could be misinterpreted.

Ian
 

Q.G.

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They (tank manufacturers like Paterson) used to sell (still do?) hoses that fit into the central column of a tank, forcing the fresh water though that center column to the bottom of the tank, displacing, from the bottom, the water at the top.
Works well.
 

clayne

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Yep. Easy to devise from off the shelf parts as well. Or just crank the faucet up.
 

Q.G.

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To be clear and precise about this, Greg: what does "change" mean here?
 

hrst

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If you want to be more precise, you could measure different amounts of dye compared to your original dose (given that you measured it!), in the same container, to find the dye concentration you can't see anymore.

It's very arbitrary what "complete change" is. Is it 10% original left, 1% original left, or 0,1% original left, or 0,01% original left?

Dye test also depends greatly on how much dye was added in the first place.

But, I'd guess these figures become irrelevant at some point. If you add enough dye that it becomes deeply colored, then you can see very small relative traces.
 

Anon Ymous

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Greg Davis said:
... However, I thought we had acetic acid in storage, but we do not...

What volume of white vinegar would I need to use in place of the 28% acetic acid?
Click to expand...

First you'll have to check the concentration of the distilled white vinegar you have, see the label. Let's assume it's a x% solution. Let F be equal to 28/x. F is a multiplication factor that you'll have to multiply with the needed volume of the 28% solution. So, if what you have is 6%, then F = 28/6 = 4,66. If you needed 125ml, then you'll have to use F*125 = 4,66*125 = 583.3ml ~= 585ml. Obviously, you'll have to adjust the water quantity at the beginning of the formula.
 

MattKing

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I'm not a chemist, but I think I can help.

The white vinegar (Heinz, FWIW) that we have here on our kitchen shelves is labelled as being 5% acetic acid.

To get the same molar quantity of acetic acid, I calculate that you need to use the following amount of vinegar:

28/5 x 125ml = 700 ml.

So I would revise the recipe to read:

175 ml water (EDIT: not 50 ml)
700 ml vinegar (5% acetic acid)
7.5 grams silver nitrate
Water to make 1L.
 
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MattKing

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Thanks Greg for doing this test.

I thought it would be useful to try to generalize the result.

I've based the following on the assumption that you are using the US gallon (128 US fluid ounces) rather than the Imperial gallon (160 imperial fluid ounces). This means that your flow rate is approximately 26 US fluid ounces per minute.

Based on that, I think I'm correct in interpreting this as saying, more generally:

a) you need to use a total volume of water equal to 9 times the volume of your tank; and
b) the water needs to flow at a rate equal to 1.6 x volume of your tank, per minute.

Can anyone see any flaw in this approach?
 

Q.G.

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Yes, thanks for the tests.

I'm not sure that the "9 times the volume of the tank" and "1.6 x volume of your tank, per minute" calculations are relevant as such, i.e. scalable in a simple/linear way.
But as you said: it's a starting 'condition', in accordance to Kodak's recommendation, for the tank you have used, and the real test is the chemical one.
 

Photo Engineer

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Kodak paper processing instructions

Here is the page from the Kodak darkroom dataguide with washing suggestions for all types of paper and that is most recent.

PE
 

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MattKing

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Thanks for catching that - I've corrected the original post.
 

MattKing

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I think it is fair to say that the "9 times the volume of the tank" and "1.6 x volume of your tank, per minute" calculations would only be reliably scalable within a fairly narrow range. I think though that they would still be useful, because that range would most likely include the sizes of commonly found roll film tanks, or suitable washers for small numbers of roll films.

In my case, I'd feel comfortable using them for every tank and washer I use (between a 350ml tank and 1200ml).
 

Photo Engineer

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Well, I ran wash tests for color paper (RC and FB), wash tests for C41 and lately wash tests of all types for film and RC and FB papers pursuant to my work on TF-5 and SuperFix. In the latest fix tests, I was comparing these two with TF-4 and KRLF with and without hardener. But who is going to believe me? So, I'm probably going to give up trying to contribute to the topics of Stops, Fixes and Washing.

PE
 

MattKing

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PE:

It's not that I don't believe you. With respect to these questions about flow and volumes of water, It's a case of how to determine whether or not what we do corresponds to what the manufacturers recommend.
 

Photo Engineer

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Matt, Greg;

Some don't believe, some do. It is best then that right now the data come from another source than me.

Here are some comments though. I was just looking at my old fixer/was tests alluded to above. They were run in 2004 and kept in a cool dark place since then. Basically, it took about a year to two years for the paper to begin to show a problem. Now, most of the underwashed results are dark brown or yellow.

Now, how to determine the best and worst conditions? It is not by the dye test. That does not tell you anything about the removal rate of hypo and Silver complexes from the coating or support (FB in this case). In fact, Kodak and several authors warn that baryta papers can retain hypo very tenaciously and actually resist washing. Wash rate also varies with volume of the wash tank and with the nature of the water supply. See the Kodak data guide I posted for the differences.

That is why all of my tests are done using the Sodium Sulfide test for retained Silver (either bad fixation OR wash) and also by using the Silver Nitrate retained hypo test. These give immediate indication of a problem, but the real result shows up only after a year or more. So, I heartily endorse using ANY wash condition that yields a "good" test with the two tests recommended. If you vary the wash, then the results WILL change. I have found that heavily aerated water will decrease wash rate at my "normal" flow rate, just by formation of bubbles on the surface of film and paper. That is why I use the Jobo washer noted above as my preferred wash method for film. It breaks the formation of bubbles on the films surface.

And, just washing 1 print or 10 prints in an 8x10 tray will change the rate of wash. For example, 8x10 prints and 5x7 prints do not wash at the same rate at the same flow rate in an 8x10 tray. The 8x10 prints will be constrained to stack, even with agitation by interleaving. The 5x7 prints will separate and drift adding to the exposure to fresh water and adding some agitation effects. However, going to 20 prints of either size in the same tray will change the 5x7 by quite a bit regarding wash rate. Try it sometime! So, the size of the tray vs print size, the number of prints, the rate of interleaving... All of this is involved. With running water, I have observed that the overall immersion / change time for a print is different than for the still method, and the number of prints used becomes a huge variable between the two methods. Simple thought experiments will help in the logic of this before you go into the lab.

There are so many factors involved that it is difficult to state. I could give a full course in this subject alone. I could write a book, believe me! And, as the guy here with a blix and a fix on sale right now (RA-RT blix first made in 1966. and TF-5, first made about 5 years ago), I can probably say that I am the only poster here with verified products on sale with a long history of sales and quality with good suggestions for processing included with them obtained by tests such as you are suggesting.

PE
 

alanrockwood

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Just out of curiosity, how did a thread on the topic of stop baths for film become transformed into a thread about final wash procedures to remove fixer?
 

clayne

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alanrockwood said:
Just out of curiosity, how did a thread on the topic of stop baths for film become transformed into a thread about final wash procedures to remove fixer?
Click to expand...

(there was a url link here which no longer exists)
 

Kirk Keyes

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One comment about using vinegar to make up the test solution - vinegar may have some sulphur compounds in it and it make cause your test solution to form a brown precipitate. If it does, don't use is and remake it with acetic acid proper.
 

Ian Grant

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With both Stop baths and washing the issue has been too many false-hoods have been posted in APUG threads recently.

All the major manufacturers state that you can use a stop bath or a water rinse for films, yet we had totally unfounded posts in another thread about how using water could lead to poor archival qualities due to residual developing compounds. This kind of false hood & speculative nonsense does no one any favours and leads to a disbelief in further postings on the subject.

When it comes to washing we were told:

"Consider this:

http://www.ilfordphoto.com/Webfiles/...1959492766.pdf on page #1. Ilford's own web site places the flowing water wash first for film - running water! The alternative using dumps is listed second and is mentioned for spiral tanks only. Kodak only gives the first method for all process conditions."

Yet Ilford say in the very next sentence that they actually recommend using their fill and dump wash technique for films processed in spiral tanks. Kodak also publish their own version of the fill & dump wash cycle in their developer data-sheets. It's this blinkered kind of attitude to being right that leads many to doubts.

In photographic processing particularly with Black & White there are often many alternatives, films, developers, dilutions, times, temperatures etc including stop baths, fixers and washing techniques all can lead to the same ultimate goals of high quality and archival permanence. There has to be a more balanced approach in forum discussion as there's not necessarily only one way which is correct, even when it comes to best archival practice.

A balanced approach acknowledges that there are differences and may also help explain why in many instances. In the case of washing Kodak dumb down and give more conservative times/volumes to cover their Sodium Thiosulphate based fixer which many use with a hardener, Ilford don't need to as their fixers are all Ammonium Thiosulphate based and they recommend no hardener is used.

The washing issue produced a very long and acrimonious thread about which way was right on another forum, it ended up being heavily moderated, a few people in this thread were at the heart of it (I'm not one of them). It took Roger Hicks to point out that both side were arguing about entirely different issues, Kodak's recommendations were based on research on Sodium Thiosulphate based fixers with a hardener and Ilford's Ammonium thiosulphate & no hardener which allows much shorter wash times.

The stop bath or water rinse issue was thrashed out here on APUG a few weeks ago. The bottom line is Ilford, Fuji and Kodak all say you can use either and what's more even advocate not using the step at all in machine processing. Only Ilford say it's preferable where possible.

Some people just haven't learnt from these previous threads here and elsewhere where they acknowledge and agreed they accept the general consensus, and then they later revert back to posting same misconceptions and half truths.

Ian
 
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