Acetic acid as stop bath for film?

[Q.G.]

Achilles and the tortoise, all over again.
A nice puzzle. But quickly disproved in practice.
It, of course, does not take millions of litres of water to wash a film as well as six changes of water do.

 

[Photo Engineer]

Kodak's present instructions for film are found here: http://www.kodak.com/global/en/professional/support/techPubs/f4017/f4017.pdf (page 6)

It says running water for 20 - 30 mins or with HCA 5 minutes.

This is with any type of fix, applied to Tri X film. The fixer time varies but not the recommended wash.

It also recommends a stop bath.

PE

 

[Removed Account2]

Achilles and the tortoise, all over again.
A nice puzzle. But quickly disproved in practice.
It, of course, does not take millions of litres of water to wash a film as well as six changes of water do.

I made an honest mistake:

The FIRST filling of the tank works exactly like the first tank filling of the fill-and-discard method.

Therefore gallons should be reduced by a factor of 1/20th. But that wasn't considered a serious error in the days we used slide rules for calculations! ) Its the principle at work here, that's important.

After that slow dissipation is the name of the game, where the film and the TANK CONTENTS soil all of the water (and film) in the tank continously.

But as you say "quickly disproved in practice" since as already stated by Ilford, 3 changes is *enough*.

When we talk about just a 1/1000th reduction (Ilford method) of concentratiuon THIS IS MEASURABLE.

Because around there is the limit where there is "enough" and "not enough".

Beyond that is more or less pointless, a concentration so small its easily soiled by part of a drop of fixer under a fingernail.

But I stand by as a fact it is not possible to reach such small concentrations with simple watering of a closed tank, for any practical amount of time-, as by 6 changes of water.

You have this all wrong, water (and fixer)---- is NOT "flushed out of the tank", instead the concentration inside the tank is slowly getting lower and lower, described as a curve, it flattens out but *never* reaches zero.

In all qualitative chemical analysis 3 changes of water was standard operating procedure, and the little vials was placed in a gravitational tumbler/spinner, to separate fluid and non-fluid.

3 changes was enough. Trying to do the same with watering out & filtration would take forever. S.O.P.

Thrust old chemists, they used to do this every day.

 

[Removed Account2]

Kodak's present instructions for film are found here: http://www.kodak.com/global/en/professional/support/techPubs/f4017/f4017.pdf (page 6)

It says running water for 20 - 30 mins or with HCA 5 minutes.

This is with any type of fix, applied to Tri X film. The fixer time varies but not the recommended wash.

It also recommends a stop bath.

PE

At what rate of running water? 1 liter per minute? half a liter per minute?

When you put numbers to that you can calculate the concentration of thiosulphate in the film that Kodak states is enough.

Enough for what? Archival purposes? 30 minutes? I doubt that very seriously
But I have seen rather convincing calculations stating that one hour is enough.

I can break out Wissenschaftliche und Angewandte Photographie from 1955 and give you a copy of the whole argument.

But I stick to 6 changes of water, save the planets water, saves my films and frankly don't give a damn about lazy geezers that don't want to be bothered by doing something right.

 

[Q.G.]

You have this all wrong, water (and fixer)---- is NOT "flushed out of the tank", instead the concentration inside the tank is slowly getting lower and lower, described as a curve, it flattens out but *never* reaches zero.

Well, something is flushed out of the tank.
And it certainly is water, 'contaminated' by fixer.
It is replaced by clean water.

If the flow rate is 1 litre per minute, a 500 ml tank will be filled with clean water, displacing contaminated water, twice per minute.

Will that have the same effect as emptying completely before filling with clean water again? Probably not.
But i will leave it to the old chemist to work out where the mistake in earlier assertions lies.
Achilles and the tortoise may help.


By the way, any homeopath will readily tell you that no matter how many times you flush your vial, the concentration will never reach zero.


Joking aside, you are too easily ignoring the fact that the dump and refill method too will not reach 'zero' concentration. Certainly not in the three times refill method you are now advocating.

 

[Photo Engineer]

The water flow rates are given in the Kodak B&W processing manuals. I have posted some of that data elsewhere on APUG along with the suggestion by EK to use a prewet for film. I have also posted the differential equation by Mason in his text "Photographic Processing Chemistry" at least twice here on APUG. It shows that a continuous wash is more effective than a series of dump and fill operations. I just don't feel like doing it again.

PE

 

[michaelbsc]

Therefore gallons should be reduced by a factor of 1/20th. But that wasn't considered a serious error in the days we used slide rules for calculations! )

1/20 isn't significant? That's 1.4 decades. Significant enough to get a red X from my old slide rule wielding P. Chem and physics task masters.

Granted that when the numbers get so big there's no practical difference. It's like the difference between a billion dollars and a trillion dollars (or insert your own currency). Both are way more than I can comprehend sensibly. Whereas the difference between a dollar and a thousand dollars is gigantic in my mind.

 

[Q.G.]

Granted that when the numbers get so big there's no practical difference. It's like the difference between a billion dollars and a trillion dollars (or insert your own currency). Both are way more than I can comprehend sensibly. Whereas the difference between a dollar and a thousand dollars is gigantic in my mind.

Hmm... I must propose some business scheme to you some time soon...

 

[nworth]

The function of a stop bath is to instantly stop development by both diluting the developer (as a rinse) and making the pH too low for the remaining developer to function. For low activity developers, a 1 percent acetic acid solution will probably work fine. In fact, a simple water rinse works fine for slow developers like D-76 or D-23. For very active developers or developers that work in a very short period of time (2 or 3 minutes), you may want something stronger. A 2 percent acetic acid solution is pretty standard for all developers, although I have seen much stronger stop baths used for extremely active developers. A 1 percent sulfuric acid solution was standard for some motion picture processes in the past.

 

[michaelbsc]

Granted that when the numbers get so big there\'s no practical difference. It\'s like the difference between a billion dollars and a trillion dollars (or insert your own currency). Both are way more than I can comprehend sensibly. Whereas the difference between a dollar and a thousand dollars is gigantic in my mind.

Hmm... I must propose some business scheme to you some time soon...

Hey, no problem. If you can get a billion dollar check from me cashed, then I\'m all over a business deal. Just don\'t expect me to take the fall for us when the cops come knocking on the door!



MB

 

[clayne]

Eric, QG pretty much summed it up. With all due respect what you're describing *is* Achilles and the Tortoise.

 

[Bill Burk]

My family won't let me mix Easter-egg dye with indicator stop bath. I'll wait until the last minute and wind up buying a gallon of distilled white vinegar because that's all that's on the shelf.

So in the spring, I'll mix household vinegar 8oz to 24 oz water for stop bath.

At that rate, a gallon goes pretty quickly. Using household vinegar is convenient, but it is not a great bargain.

 

[Photo Engineer]

Make sure you use white vinegar!

PE

 

[clayne]

My family won't let me mix Easter-egg dye with indicator stop bath. I'll wait until the last minute and wind up buying a gallon of distilled white vinegar because that's all that's on the shelf.

So in the spring, I'll mix household vinegar 8oz to 24 oz water for stop bath.

At that rate, a gallon goes pretty quickly. Using household vinegar is convenient, but it is not a great bargain.

Kodak Stop-Bath is incredibly cheap. You aren't using it 1-shot are you? If so, that's a huge waste. Stop-bath is probably the long-lasting of all the standard chemicals in mixed form.

 

[Ian Grant]

The water flow rates are given in the Kodak B&W processing manuals. I have posted some of that data elsewhere on APUG along with the suggestion by EK to use a prewet for film. I have also posted the differential equation by Mason in his text "Photographic Processing Chemistry" at least twice here on APUG. It shows that a continuous wash is more effective than a series of dump and fill operations. I just don't feel like doing it again.

PE

The final paragraph is Levensons work where he writes that staged washing is the most efficient way to reduce the residual thiosulphate level below the recommended minimum levels.

Staged washing is where the tank is emptied at least three times during a wash cycle with quite as slow continuous flow rate. It's difficult to relate to individual film processing but was a rate of 10 litres per 10000ft of film, but it's around 33ml per roll of 35mm/120.

6 washes of 300ml per 35mm film is 1800nl and by both Levensons & Masons figures as Erik indicates gives far more dilution than the minimum required.

Ian

 

[alanrockwood]

Acid stop bath vs. water stop bath is a controversial topic. Actually, using water as a stop bath works just fine and is recommended by some makers of processing equipment, such as Photo-therm.

Acid stop bath works fine too. It just costs a little more and smells bad.

As to whether it is essential to instantly stop development of the film, that too is controversial. However, what really counts is that the system is reproducible, and a water stop bath can be reproducible.

As to the timing of the development development step, water does not provide as fast of a stop as acetic acid, so film continues to develop for a short time after it is placed in the water stop bath. If that is seen as a problem then just reduce the processing time a smidge to compensate.

Bottom line; use either water or acid stop bath. Either will work fine once you have your process dialed in.

 

[clayne]

It smells great!

I'm all for a debate about whether a stop bath should have great taste or less filling, as well...

 

[clayne]

The final paragraph is Levensons work where he writes that staged washing is the most efficient way to reduce the residual thiosulphate level below the recommended minimum levels.

Staged washing is where the tank is emptied at least three times during a wash cycle with quite as slow continuous flow rate. It's difficult to relate to individual film processing but was a rate of 10 litres per 10000ft of film, but it's around 33ml per roll of 35mm/120.

6 washes of 300ml per 35mm film is 1800nl and by both Levensons & Masons figures as Erik indicates gives far more dilution than the minimum required.

Ian

So you're telling me if I drill a hole in the bottom of the tank and place it under the running faucet I'm not going to have the same result as filling it up and emptying it out, repeat?

 

[Ian Grant]

I'm not telling you, that's what Levenson is saying

Essentially he's saying that if you were to use/make a film washer as you suggest then stopping the flow & letting it empty 3 times during the wash cycle increases efficiency, but then he's talking about trying to cut total water usage on a much larger scale of processing - so more efficient use of water.

The issue is that constant dilution can be less efficient and require substantially more water. It's less relevant when processing a small number of films.

Ian

 

[clayne]

Sure, I could see that being the case where said water has additional solution capacity. I can't see the 66M litre argument though.

 

[Photo Engineer]

P 204, Mason ".......separate washes are fed continuously with fresh water...."

To summarize about 5 pages, the best wash is to have several wash tanks with water flowing from last to first, but if you wish to conserve water you can use individual washes in 1 tank, but he then goes on to point out that in this case you have to use a rather large wash tank with a lot of water and the size is dependent on the number and sizes of the film/paper being washed.

So, to some extent, Mason has been misread. He does recommend running water, but in separate tanks, with counter current flow from last to first or changes of water in one tank with a large tank so as to dilute the hypo very well.

He states further that if you use 3 stage washing you should use a continuous flow of 10 liters per 1000 ft of 35 mm film and you must have efficient squegees to use on the film (or paper) between stages. Mason attributes part of this to Levenson, and states that the carryover in 3 or 4 wash systems (dump and refill) is significant and the film must be squegeed! All of these details seem to be missed or glossed over when quoting Mason.

One gets down to the fact that a continuous wash with running water and good agitation appears to be his first choice. The Kodak reference says the same!

PE

 

[Ian Grant]

Mason's comments are to some degree rather irrelevant because he's not describing small scale washing of 1 or a small number of films, rather washing in a continuous processing unit.

So when quoting from Mason one needs to take that into account. A flow rate of 10 litres per 1000ft of film is 33ml (approx) per film, he's taking about using minimal volumes of water, hence the need for squeegeeing between each wash bath.

When we wash a film in a dev tank or separately we need larger volumes of water typically 300-500ml to fill a tank to cover the film spiral. As Erik pointed out back in (there was a url link here which no longer exists) the dilution is more important as far as we are concerned with small numbers of films.

Ian

 

[Photo Engineer]

Mason is either relevant or irrelevant. Which is he? He is the supposed source of the dump wash method. It either is or is not valid. It is valid with large wash trays and squegees according to him. But ignore him and go to the Kodak web site. They give much the same advice even for small tanks!

PE

 

[Ian Grant]

Mason & Levenson were still actively working on wash techniques at the time of publication. You have to take the relevant parts out from the rest and put them in context with both Ilford & Kodak's separate wash cycles for small scale & amateur use where a tank is filled, agitated and the water dumped after a short period of time before refilling.

The roots for the later published techniques is in that Mason section, but as that section's written it's not all directly relevant to our very much smaller scale use.

Ian

 

[Photo Engineer]

Guys;

If you look at the Kodak technical publication, you will see that there is just one recommendation for washing film. If you go to the Kodak B&W manual you will see only one recommendation. That is continuous running water. Mason says the same using a cascaded counterflow of water in 3 large tanks with moving film, or running water in a large tank in other cases. He suggests squegees in the case of using the dump method.

You cannot pick and choose and you cannot arbitrarily select and reject what you don't want to hear or accept.

Consider this:

http://www.ilfordphoto.com/Webfiles/20062101959492766.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.

I do not try to set myself up as a super expert in this, I use texts (Mason and Haist) and authoritative web sites such as Kodak and Ilford. I must add that I spent 5 years working on bleaches, fixes and the subsequent wash step, so I do have some analytical and R&D background to back up what I believe to be the correct methods. For this, I refer you to Haist, V1, P664, 2nd and 3rd paragraphs. Running water with agitation minimizes time of treatment, dumps take longer but use less water. All texts beg the question of these two differences, time and volume used. Mason says that rather large volumes are needed in the dump method along with a squegee as mentioned above.

PE