Acetic acid as stop bath for film?

Q.G. · Oct 17, 2010

Erik Prestmo said:
But you fezzed up and said you never saw the picture, so whats the big deal?

If you keep asking questions...

The big deal is that you have produced a set of nonsensical comments about that picture, illustrating that you don't understand how things work.
You see, it's quite irrelevant whether i have or have not seen the picture: your comments i most certainly have seen.

But it's quite clear now that you're not interested in how things work. So why do you bother talking about that picture?

Removed Account2 · Oct 17, 2010

Interesting sidetrack: to clean the frozen rangefinder om a Agfa Isolette III I used Hoppes no. 9 from my gun cleaning cabinet.
It is formulated to get rid of verdi gris among other stuff, and works well on intricate brass thingies..... if you smell it, you recognize it.

Photo Engineer · Oct 17, 2010

Back to Stops

On the more mundane and currently OT subject of Stops, I have been reviewing Anchell and Troop, most particularly page 103 on Stops in Chapter 12.

I have discussed these points with Bill personally and also with 4 fellow Kodak engineers including Grant Haist. Here is the consensus.

1. pH variations generate heat and can cause grain clumping.

This was an early theory which has never been proven anywhere. Energy calculations based on concentration preclude that sufficient heat be generated. Therefore, this is dismissed by all with whom I have discussed it. The theory stands as unproven in any way.

2. Acid Stop can cause pinholes with carbonate developers.

First advanced by the book on photo processing chemistry by George Eaton in the 50s, this has only been seen in deep tanks with films before and in the 40s. It seems that the deep tank will allow for formation of CO2 gas in film and that hydrostatic pressure in the deep tanks of photofinishers would restrain release of the gas. When the film was quickly raised out of the Stop the gas would release causing pinholes. It was never seen in small tank, tray or any other method and never seen in the 60s or later with harder films.

I have personally tested films and papers from 68F to 120F in Carbonate developers during our conversion from Borate to Carbonate in the 60s, and have seen no problem using a stop. Kodak now uses Carbonate developers for all color products at up to 100F and a following Stop causes no problems.

3. Acid Stop may cause excessive swell.

This was true about 100 years ago with Pig Gelatin based photo products. Today, using Bone (Cow) gelatin and polymers, this is not true. In fact, the conversion took place in the 50s - 60s.

See the attached curve for swell vs pH.

Bill and I had planned on including a larger revised and corrected section on Stop Baths in a revised edition of Anchell and Troop but this will probably never take place. Portions of this have been posted elsewhere.

PE

Q.G. · Oct 17, 2010

PE,

If we skip the acid stop, rinse in water instead, and then drop the film in acid fix, would that not give the same concern about these (whether real/big enough or not) problems arising?
I.e. if these issues were raised against using an acid stop bath, would that then not be a red herring?

Ian Grant · Oct 17, 2010

I won't comment on third party books

Remember that there's still some older emulsions floating around, like Fortepan 200 & 400 (also sold as Classic Pan & Bergger) these are the last re-incarnation of 1939 Kodak Super-X and Tri-X which Kodak manufactured at their factory in Hungary - which became Forte after WWII, and also poorly hardened emulsions from EFKE. These films can suffer pinholes with carbonate developers and a strong acid stop-bath in any tank or tray, it doesn't have to be a deep tank.

When Eaton wrote his book all commercial labs & photographers developed in deep tanks with plates or films in in holders so any issues were more likely to be seen there.

I don't think Eaton was the first to mention the Carbonate / Stop bath / Pinhole / gas theory, I think it goes back a long way. By the 50's few were using the older strong developers with high carbonate levels. But it's interesting that the manufacturers say water rinse on the boxes of those old emulsions at a time (1900's to 1930's) when stop baths were used in other applications, they don't say either or.

It's like reticulation or grain clumping/micro-reticulation not all films are equal, it's probably the same films that will suffer in both cases due to ether being thick emulsions or poorly hardened or a combination of both.

Ian

Ian Grant · Oct 17, 2010

Q.G. said:
PE,

If we skip the acid stop, rinse in water instead, and then drop the film in acid fix, would that not give the same concern about these (whether real/big enough or not) problems arising?
I.e. if these issues were raised against using an acid stop bath, would that then not be a red herring?

Many scid fixers aren't that acidic - pH 5.2 (Hypam or Kodak Rapid Fixer) is not remotely like the pH 2.9 & 2.2 of acetic acid and citric acid Stop baths, the order of magnitude in the difference is very large as pH is a log scale.

some stop baths are buffered to higher pH's.

Ian

Photo Engineer · Oct 17, 2010

The pH of Vinegar is about 2.9 and is about a 1 molar solution (5% - 6%). Stops are in the range of 1% - 2% and are therefore much weaker than that and have lower buffer capacity. Many Stops are found to be in the pH range of 3.5 - 4.5 and many acid fixes are in the range of 4.5 - 5.5. Above that point, the fix is generally considered neutral in pH. A Stop must not be above 2% in concentration for good results.

The generation of Carbon Dioxide can take place in either a Stop or an acid Fix at pH values from 3.5 up to about 5.5. Above that, much of the CO2 will tend to stay in the water. The formation of pinholes from outgassing was never demonstrated to take place in tank or tray processing in any way with any film.

The matter of gelatin swell noted above is based on type of gelatin. Manufacturers use mainly bone Gelatin, not pig Gelatin. So the argument of swell vs pH is not one of hardness per se, but rather one of the type of gelatin used. Only the manufacturers can tell us for sure what type of gelatin is used. Kodak uses Bone Gelatin, Ilford and Fuji appear to use Bone Gelatin. The majority of photograde gelatins made today are Bone Gelatin. QG, I refer you back to a previous post here on swell vs pH.

I have fully discussed this item elsewhere and have discussed it with Bill both in person, on the phone, and on-line. Ian, you have commented here on 3rd party books many times. My opinion of A&T is very high. I merely point this one bit out as an exception that would have been fixed in a new edition.

In no case has the neutralization been shown to cause problems with clumping nor is there any excessive heat in the emulsion. In fact, one of the engineers broke out in a fit of laughter when I brought it up. It is classed as "one of those old myths"!

PE

billtroop · Oct 18, 2010

OK, OK, Ron, enough! I accept what you say on this point. But the point was given to me by Grant, so I thought it was worth running with. Both of us wanted to promote alkaline fixing and used every argument there was. Some of the arguments are good, some are less good, and this is one of the less good. Most people here wouldn't know what an uphill battle it's been to get neutral-to-alkaline fixing accepted at all. But it has been. Even in 1998, the year FDC came out, many of those who read the manuscript thought I was nuts to discuss it. Zawadzki, Dickerson, and Crawley just did not like it. And remember I already had my alkaline fixer formula out on the market for a decade before that. I would never have had the courage to do that had it not been for the encouragement of Haist and HD Russell. By the way, I join you in the hope that Steve Anchell will let us do a second edition of FDC together - - it would be fantastic to be working directly with someone of your calibre. Steve, are you listening? Pretty please?

nworth · Oct 18, 2010

First, the developers that caused the pinhole problems had high concentrations of carbonate, and this problem was only seen in some deep tank situations. Neither of these conditions is common today. Most developers either do not use carbonate or are highly diluted, and most people use small tanks. Second, the purpose of the stop bath is to instantly stop the development by lowering the pH and to provide a rinse to remove residual developer. If you calibrate your development, you may not need to instantly stop development, and a couple of rinses in water will remove the developer. The important thing with this method is to be consistent.

Removed Account2 · Oct 18, 2010

Stops and carbonate concentrations.....
I was thinking about Caffenol-C which has a soda (carbonate) base, @ 40 grams of soda per liter that is 4% soda, I dunno if that is considered high today?

Anyways there have been reports of spots, maybe not pinholes, but PE : could that be because of CO2?

There are lots of people trying to wrangle the CC-M and CC-L mixes into reliable developers, and any source of error needs to be addressed.

Since developing times are long in all CC mixes, I maybe have an answer to my question myself, pro'lly none of these are hig conc. developers?

And since developing times are long one really do not need a stop, its easy to be consistent without a stop - I still use it, out of old habit.

Any thoughts on that?

Photo Engineer · Oct 18, 2010

Pinholes caused by CO2 appear as craters using magnification. They actually blow the emulsion away. I have only seen them in unhardened coatings or in archival micrographs.

Pinholes from airbells do not cause disruption of the gelatin matrix.

PE

billtroop · Oct 20, 2010

I really don't know why people insist on saying that an acetic acid stop bath 'instantly' stops development. It doesn't. It takes about 30 seconds. A 10% buffered acetic acid/sodium acetate stop bath stops development in 3 seconds. It's all on p. 104 of FDC, summarized from Haist who summarized from the only study the industry has seen fit to commission in its entire history which leads one to presume that the study is probably still correct. The important thing to consider in stopping development is not pH, but total acidity. I would have predicted that in 2010, people would be figuring out how to make and use alkaline stop baths, but then, I have never been good at prophecy.

nworth said:
First, the developers that caused the pinhole problems had high concentrations of carbonate, and this problem was only seen in some deep tank situations. Neither of these conditions is common today. Most developers either do not use carbonate or are highly diluted, and most people use small tanks. Second, the purpose of the stop bath is to instantly stop the development by lowering the pH and to provide a rinse to remove residual developer. If you calibrate your development, you may not need to instantly stop development, and a couple of rinses in water will remove the developer. The important thing with this method is to be consistent.

Ray Rogers · Oct 21, 2010

G'Day!

billtroop said:
I really don't know why people insist on saying that an acetic acid stop bath 'instantly' stops development. It doesn't. It takes about 30 seconds.

Which, IIRC, is a typical stop bath time....
and which also means plain water is probably significantly slower....

billtroop said:
A 10% buffered acetic acid/sodium acetate stop bath stops development in 3 seconds.

The two above stops (30 sec vs 3 sec.) are at the same pH?

billtroop said:
The important thing to consider in stopping development is not pH, but total acidity.

Are you talking about buffer capacity vs pH?

Photo Engineer · Oct 21, 2010

I posted the information from Haist earlier.

PE

Ray Rogers · Oct 21, 2010

helpful for those w/o a copy of FDC

BTW Congratulations on being an instructor again...
(better snow than pepper!)

Gerald C Koch · Oct 21, 2010

Ray Rogers said:
G'Day!

Which, IIRC, is a typical stop bath time....
and which also means plain water is probably significantly slower....

This is a diffusion controlled reaction and its speed is determined by the rate of diffusion of stop bath into and developer out of the emulsion. It is arguable whether the composition of the stop bath (plain water or conventional stop) has any appreciable effect on the speed of stopping development.

Now concerning this thread as a whole and its various contributers and commenting only on stopping development. Using an acid stop bath vs plain water is more like an act of religious faith. It divides photographers into two camps. Neither side will concede to the other. But the paucity of actual data about this question in the standard photographic texts speaks volumes about its relative importance. For film and RC paper, use whatever method which makes you most comfortable.

This issue has continued ad nauseam in so many posts over the years. It's like Coke and Pepsi trying to get you to come over to their product. It just ain't going to happen. Please all, enough. give it up.

Photo Engineer · Oct 21, 2010

The one and only study of stopping rate vs pH and buffer capacity was re-reported in Haist (see my earlier post) and re-re-reported in A&T as noted by Bill above. This is the one and only study AFAIK and as far as Bill knows. It still stands. It illustrates all points regarding stop rate of acid, acid + buffer, acid vs pH and acid + buffer vs pH. This study shows rates of stopping power vs pH and buffer capacity and illustrates that development may not stop as soon as you wish and therefore, stop may be useful in having a repeatable process and that is why most publications recommend it for film and state that it is preferred for paper which develops more rapidly.

PE

Ray Rogers · Oct 21, 2010

Well!

JFYI Pepsi tastes MUCH better than Coke!
It has a stronger cinnamon note and is overall, simply more flavorfull!

As for as stop baths and short stops, I think it should be quite easy to devise a sensitometric test to demonstrate and quantify once and for all those presumed changes.

Remember though, the reason we have these senseless endless threads anyway is that the effect is small and not one easily observed by casual observaton... at least with the normal material and procedures in current use. In that sense you are right, but the concept is I think, valid and might apply even more strongly to certain now obsolete (or expermental!) materials.

Ray Rogers · Oct 21, 2010

Gerald C Koch said:
Using an acid stop bath vs plain water is more like an act of religious faith.

:joyful: Amen.

Gerald C Koch · Oct 21, 2010

Mason predates Haist in saying that development may continue into the fixing bath even with the use of a stop bath. The use of an acid stop bath does however extend the life of the fixer. But the main argument of this thread, as I interpret it was, the stopping of development. But enough said.

Ray Rogers · Oct 21, 2010

Maybe his short stops were too short?

But despite Brevis esse laboro, obscurus fio I agree. Enough said!

Photo Engineer · Oct 21, 2010

Ray;

Pepsi has a slight flavor of camphor too!

Ray, Jerry;

The effect of a wash compared to stop will vary with film, developer, fix and also the type of rinse water used between the developer and fix. So, this is not an easy subject to pin down. In the long run, stop will be more repeatable and rinse will be more variable. That is the only point here.

And, over the years I have been here, believe me, process variability is not a trivial complaint. Trying to pin it down is hard!

PE

nworth · Oct 22, 2010

billtroop said:
I really don't know why people insist on saying that an acetic acid stop bath 'instantly' stops development. It doesn't. It takes about 30 seconds. A 10% buffered acetic acid/sodium acetate stop bath stops development in 3 seconds. It's all on p. 104 of FDC, summarized from Haist who summarized from the only study the industry has seen fit to commission in its entire history which leads one to presume that the study is probably still correct. The important thing to consider in stopping development is not pH, but total acidity. I would have predicted that in 2010, people would be figuring out how to make and use alkaline stop baths, but then, I have never been good at prophecy.

Agreed.

Photo Engineer · Oct 22, 2010

Gerald C Koch said:
Mason predates Haist in saying that development may continue into the fixing bath even with the use of a stop bath. The use of an acid stop bath does however extend the life of the fixer. But the main argument of this thread, as I interpret it was, the stopping of development. But enough said.

Mason may state that, but Haist shows data. And he shows how to prevent any continuing development action.

PE

Q.G. · Oct 22, 2010

I have some ancient literature in which stop baths don't even figure, explaining that the acidity of the fix is only there to stop development.

Why would it be a problem that development carries on into the next step?
As long as we know how to use the process to get good results.
PE, you have mentioned consistency, and that's a good one. Not that i have ever noticed anything bad in that respect.

It would seem to me that a stop (or a water rinse) was introduced at one time just as a step that prolonged the fixer's working life.

Acetic acid as stop bath for film?

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