Stop Bath.. How important?

MattKing · Nov 27, 2023

One of the reasons I advocate use of a stop bath is that it is less likely to be used incorrectly than water.
An effective water stop needs to employ flowing water or several changes of fresh water - not just a dunk in water and then off to the fixer.
For those of us with experience doing this stuff, and know how to properly employ a water stop, the results are probably interchangeable - save some possible saving on fixer.
For those beginners who are trying to learn from instructions and the internet, the manufacturer's recommendations which recommend stop bath make more sense.
And of course, while methods that are designed for commercial labs may be more than necessary when employed by a small volume user, if they are simple and easy to employ - as stop bath is - they make a lot of sense.

Philippe-Georges · Nov 27, 2023

Does a water stop bath must be 'running' water?

What I do for a few weeks now, is filling the tank with water, at the same temp. as the developer, and 'run' it on a motor base for 2 min., then discard and fix with a neutral-to-alkalic fixer (Fuji-Hunt's Unilec 1+4) in two baths for 2 min. each.

I didn't notice any difference, nor issues, as when I used a buffered stop.
But, I have to admit, I didn't test with a densitometer, why would I as I was pleased with the results: simplicity, no more mixing Sodium Hydroxide and Acetic Acid, no difference in printing on first sight and (hopefully-) less pollution.

PS: perhaps someone can help me out here: I vaguely recall to have read somewhere that, when using a water stop, the development stil continues a little in the low lights, as there the developer isn't exhausted yet, but doesn't in the highlights.
Sadly I don't recall where I read it, and I don't know the value of this statement (but I hope it is true)...

MattKing · Nov 27, 2023

Philippe-Georges said:
Does a water stop bath must be 'running' water?

To be fully effective, you need a water stop to both dilute the developer and carry the diluted developer away.
You would be better off changing the water a couple of times and running the agitator for a shorter time each time.
I'm not sure why you add sodium hydroxide to the diluted acetic acid.

Philippe-Georges · Nov 27, 2023

MattKing said:
To be fully effective, you need a water stop to both dilute the developer and carry the diluted developer away.
You would be better off changing the water a couple of times and running the agitator for a shorter time each time.
I'm not sure why you add sodium hydroxide to the diluted acetic acid.

The Sodium Hydroxide is added as an alkalic buffer to make a less acetic stop pH6 when Pyro H-D developing as Sandy King advised.
The formula I used was by Ryuji Suzuki.

But now a apply a water stop...

Anon Ymous · Nov 27, 2023

MattKing said:
I'm not sure why you add sodium hydroxide to the diluted acetic acid.

Theoretically, you could make a buffered stop bath by mixing acetic acid with some sodium hydroxide (or some other alkali for that matter). This would have a greater capacity, but IMHO it gets too convoluted for no serious reason. I mean, you can always use an indicator stop bath and be done with it anyway, it takes no time to mix another batch when needed.

koraks · Nov 27, 2023

Anon Ymous said:
Theoretically, you could make a buffered stop bath by mixing acetic acid with some sodium hydroxide (or some other alkali for that matter).

It'll make itself. Just start with an acetic acid stop bath (or citric acid if you prefer), use it once and hey presto...it's a buffered stop bath!
This is why 'weak' acids are also preferred as stop baths, I think. They buffer themselves, basically (or...acidicly?)

Anon Ymous · Nov 27, 2023

koraks said:
It'll make itself. Just start with an acetic acid stop bath (or citric acid if you prefer), use it once and hey presto...it's a buffered stop bath!
This is why 'weak' acids are also preferred as stop baths, I think. They buffer themselves, basically (or...acidicly?)

Lol, that's exactly what I'm thinking when I see anything about buffered stop baths. Anyway, perhaps @Philippe-Georges wants to make a weaker stop bath in order to preserve the stain from Pyrocat HD, but that too is debatable. In any case, a water stop bath for BW film works just as well...

JerseyDoug · Nov 27, 2023

Has anyone here seen a genuine problem when using a quick plain water stop bath while developing film that went away when they switched to a commercial stop bath?

By a quick plain water stop bath I mean something like pouring out the developer, pouring in plain water, inverting the tank continuously for 30 seconds, pouring out the water, pouring in the fixer and initiating agitation. I develop with Rodinal 1:50 which usually takes about 12 minutes so the time the stop bath takes is pretty much negligible. FWIW I've been doing this for 60+ years.

john_s · Nov 27, 2023

Philippe-Georges said:
The Sodium Hydroxide is added as an alkalic buffer to make a less acetic stop pH6 when Pyro H-D developing as Sandy King advised.
The formula I used was by Ryuji Suzuki.

But now a apply a water stop...

The point then was that Ryuji Suzuki used a Nova vertical slot processor for printing and he preferred to replace all three liquids at the same time for convenience. The Nova version he used did not have drain taps at the bottom. The buffered stop bath had a greater capacity than acetic acid solution alone. He also said something about it being better for the paper to have the pH not as low as acetic acid solution.

RalphLambrecht · Nov 27, 2023

dancqu said:
My tap water is as alkaline as some developers I've used.

that wold worry me if true and would certainly be worth a call to the water department.

Philippe-Georges · Nov 28, 2023

Yesterday evening, I dug into Anchell & Troop's 'The Film Developing Cookbook' again, and chapter 12, particularly pages 103 and 104, were very interesting.
Although, it does not concern paper processing in particular, it was rather enlightening and their theory could be applied to a lot of different B&W processing.

Then I toke AA's 'The Negative', and there he talks about negative developing and water baths, although not intended as a stop bath, it is interesting too, but I wonder if this can be fully applied on the nowadays thin emulsion films.
AA advocates an acetic stop bath.
I still have to dug into AA's 'The Print'...

Carnie Bob · Nov 28, 2023

JerseyDoug said:
Has anyone here seen a genuine problem when using a quick plain water stop bath while developing film that went away when they switched to a commercial stop bath?

By a quick plain water stop bath I mean something like pouring out the developer, pouring in plain water, inverting the tank continuously for 30 seconds, pouring out the water, pouring in the fixer and initiating agitation. I develop with Rodinal 1:50 which usually takes about 12 minutes so the time the stop bath takes is pretty much negligible. FWIW I've been doing this for 60+ years.

Not with film but with lith prints yes I have seen a difference , with water the develpment snatch time changes, with acid stop the snatch time is clearly defined.

Rolleiflexible · Nov 28, 2023

MattKing said:
One of the reasons I advocate use of a stop bath is that it is less likely to be used incorrectly than water.
An effective water stop needs to employ flowing water or several changes of fresh water - not just a dunk in water and then off to the fixer.

JerseyDoug said:
Has anyone here seen a genuine problem when using a quick plain water stop bath while developing film that went away when they switched to a commercial stop bath?

In college, I learned to stop development with a simple water rinse: Dump the developer, fill with water, agitate a few times, dump the water, add fixer. Five decades later, that is still my routine.

We all have our eccentricities in our workflows. I am sure that obsessing over stop baths gives comfort, like a stuffed animal or a security blanket. But I cannot see any need in my own experience to support it. FWIW, I have always developed in Rodinal or HC-110.

Vaughn · Nov 28, 2023

Rolleiflexible said:
In college, I learned to stop development with a simple water rinse: Dump the developer, fill with water, agitate a few times, dump the water, add fixer. Five decades later, that is still my routine.

We all have our eccentricities in our workflows. I am sure that obsessing over stop baths gives comfort, like a stuffed animal or a security blanket. But I cannot see any need in my own experience to support it. FWIW, I have always developed in Rodinal or HC-110.

That is what our procedure at the university darkroom I learned at, volunteered at, and eventually worked at. A period of several decades. No stop bath in the film developing room...just three exchanges of water through their SS tanks. Up to 125 students a quarter. Not using stop bath was never an issue, and one less chemical to deal with. Stop bath was used in the room where sheet film was developed...easier in the dark than using running water of multiple exchanges (on SS racks in 1 qt SS tanks).

alanrockwood · Nov 28, 2023

JerseyDoug said:
Has anyone here seen a genuine problem when using a quick plain water stop bath while developing film that went away when they switched to a commercial stop bath?

By a quick plain water stop bath I mean something like pouring out the developer, pouring in plain water, inverting the tank continuously for 30 seconds, pouring out the water, pouring in the fixer and initiating agitation. I develop with Rodinal 1:50 which usually takes about 12 minutes so the time the stop bath takes is pretty much negligible. FWIW I've been doing this for 60+ years.

I have not seen any reports of genuine problems for film development, although earlier today in this thread Carnie Bob reported problems with lith print development when using water-based stop bath.

All of the reports of I have seen (for film development) that were based on actual experiments (of which there are a few that can be found on the internet, but not very many) reported no significant difference. One of them did actual densitometry testing. I misplaced the link for that one, so I can't supply the link right now.

Note added later: I found the link to one of the tests. Go to this link https://www.flickr.com/groups/84061069@N00/discuss/72157632984029014/ and read the second post by Convict J-man. He gives a very brief description of his comparison test of water stop bath vs. acid stop bath. In brief, he used a sensitometer to expose a step wedge, an automated processor to process the negatives, and a densitometer to read the densities. He did the test using extremely short development conditions, using a developer that developed most films to normal contrast in about 45-60 seconds, which are extreme conditions that would maximize the probability of seeing a difference between the two types of stop bath. The bottom line is that he saw no more than a trivial between acid stop bath and water stop bath.

Sirius Glass · Nov 28, 2023

Vaughn said:
That is what our procedure at the university darkroom I learned at, volunteered at, and eventually worked at. A period of several decades. No stop bath in the film developing room...just three exchanges of water through their SS tanks. Up to 125 students a quarter. Not using stop bath was never an issue, and one less chemical to deal with. Stop bath was used in the room where sheet film was developed...easier in the dark than using running water of multiple exchanges (on SS racks in 1 qt SS tanks).

Yes, it is possible to substitute water for stop bath and I have used water to temporarily stop print development for examination and then used developer to selectively continue development of a small area of a print, but I still follow with stop bath before fixing the print. Stop bath helps prolong the life of fixer as well as quickly halting the development. Why would Kodak, Ansco and others have spent large amounts of time and money for research and development on stop bath if stop bath were not necessary? The manufacturers had proven to themselves that stop bath was necessary for the darkroom and then proceeded to develop the best stop bath they could produce. What is they know that you have chosen to ignore? Please consider that before recommending always avoiding stop bath.

Vaughn · Nov 28, 2023

Sirus -- we used stop bath in the printing room. Only in the roll film developing room was stop bath not provided.

Mick Fagan · Nov 28, 2023

In the graphic arts world, where we were producing halftone film for magazine reproduction in high temperature roller transport processors, having a stop bath was a requirement for consistency.

For newspaper reproduction, with their coarse dot size, it wasn't really a problem, however for magazine and poster reproduction where the starting point is 150 DPI and upwards to generally 300 DPI, very precise processing was a requirement.

Not to mention 4 colour 300 DPI colour separation negatives, where dot size consistency is paramount.

In general, the run of the mill roller transport processors with which we did halftone film processing, were our smaller machines, somewhere around 650mm wide, the biggest stuff these had go through would have been a double page spread with a gutter bleed on a broadsheet newspaper, which from memory was 56cm deep by 108 ems wide on the image area, although I could be slightly out.

For pure line artwork, we had some larger processing machines for our largest camera, which was capable of exposing 1 metre square film per exposure, not exactly sure just how wide they were, but they were big.

To give a bit of perspective, the film was exposed through a glass plate which had a grid of straight lines running at 300 lines per inch in a vertical and horizontal pattern.

The camera operator would photograph the image, then using a loupe to check dot size, the operator could ascertain if more or less exposure was required; processing always stayed the same.

A midtone dot was where 50% of the square was white and 50% of the square was black, highlight dots were where 10% of the square was black and 90% of the square was white. Shadow areas required 90% of the square to be black and 10% of the square to be white. Obviously there were in-between gradations, but this should explain why stopping film development exactly at a predetermined time was a requirement for success.

This was in the seventies and eighties and running through to the mid nineties, which was when electronic halftone conversion of continuous tone pictures was happening in ever increasing numbers.

Rolleiflexible · Nov 28, 2023

Mick Fagan said:
For newspaper reproduction, with their coarse dot size, it wasn't really a problem, however for magazine and poster reproduction where the starting point is 150 DPI and upwards to generally 300 DPI, very precise processing was a requirement.

I learned in the darkroom of the college newspaper. I've never had an issue using water.

alanrockwood · Nov 28, 2023

Mick Fagan said:
In the graphic arts world, where we were producing halftone film for magazine reproduction in high temperature roller transport processors, having a stop bath was a requirement for consistency.

For newspaper reproduction, with their coarse dot size, it wasn't really a problem, however for magazine and poster reproduction where the starting point is 150 DPI and upwards to generally 300 DPI, very precise processing was a requirement.

Not to mention 4 colour 300 DPI colour separation negatives, where dot size consistency is paramount.

In general, the run of the mill roller transport processors with which we did halftone film processing, were our smaller machines, somewhere around 650mm wide, the biggest stuff these had go through would have been a double page spread with a gutter bleed on a broadsheet newspaper, which from memory was 56cm deep by 108 ems wide on the image area, although I could be slightly out.

For pure line artwork, we had some larger processing machines for our largest camera, which was capable of exposing 1 metre square film per exposure, not exactly sure just how wide they were, but they were big.

To give a bit of perspective, the film was exposed through a glass plate which had a grid of straight lines running at 300 lines per inch in a vertical and horizontal pattern.

The camera operator would photograph the image, then using a loupe to check dot size, the operator could ascertain if more or less exposure was required; processing always stayed the same.

A midtone dot was where 50% of the square was white and 50% of the square was black, highlight dots were where 10% of the square was black and 90% of the square was white. Shadow areas required 90% of the square to be black and 10% of the square to be white. Obviously there were in-between gradations, but this should explain why stopping film development exactly at a predetermined time was a requirement for success.

This was in the seventies and eighties and running through to the mid nineties, which was when electronic halftone conversion of continuous tone pictures was happening in ever increasing numbers.

Very interesting. Was a water-based stop bath tested in these applications, or perhaps more to the point, did anyone ever try to optimize the process for a water-based stop bath rather than acid-based stop bath?

One reason I ask is because the issue of consistency keeps being brought up. However, I can't think of a physical reason why an acid-based stop bath would necessarily produce more consistent results than a water-based stop bath. Of course, like my old research adviser used to say "theory proposes, experiment disposes."

GLS · Nov 29, 2023

Just use a ~ 1% solution of citric acid as stop. Food grade citric acid is incredibly cheap, has no smell, and the solution can be mixed up fresh in seconds.

Mick Fagan · Nov 29, 2023

alanrockwood said:
Very interesting. Was a water-based stop bath tested in these applications, or perhaps more to the point, did anyone ever try to optimize the process for a water-based stop bath rather than acid-based stop bath?

One reason I ask is because the issue of consistency keeps being brought up. However, I can't think of a physical reason why an acid-based stop bath would necessarily produce more consistent results than a water-based stop bath. Of course, like my old research adviser used to say "theory proposes, experiment disposes."

In a word, No!

I do understand where you are coming from, but in a large commercial operation where film throughput is ginormous, you pretty much remove as many variables as possible. To put things in perspective, film deliveries for our B&W lithographic stuff, were at least once a week, sometimes twice using trucks and requiring forklifts to unload. We also had DuPont technicians coming in at least once a week to ensure all of our processors were fully maintained and in optimal (chemistry wise) condition.

I guessing here, but in the City of Melbourne, I would think we had somewhere around 30 to 40 film processors, just for B&W film spread through our various trade houses.

Don_ih · Nov 29, 2023

alanrockwood said:
Was a water-based stop bath tested in these applications, or perhaps more to the point, did anyone ever try to optimize the process for a water-based stop bath rather than acid-based stop bath?

Given Mick's description of the vast amount of film being processed, water would be inefficient. You would need constant fresh water for the stop bath for it to be effective. An acid stop can be contained in a closed process, so the only waste water is the rinse water.

john_s · Nov 29, 2023

Mick Fagan said:
In a word, No!

I do understand where you are coming from, but in a large commercial operation where film throughput is ginormous, you pretty much remove as many variables as possible. To put things in perspective, film deliveries for our B&W lithographic stuff, were at least once a week, sometimes twice using trucks and requiring forklifts to unload. We also had DuPont technicians coming in at least once a week to ensure all of our processors were fully maintained and in optimal (chemistry wise) condition.

I guessing here, but in the City of Melbourne, I would think we had somewhere around 30 to 40 film processors, just for B&W film spread through our various trade houses.

That really brings home the economies of scale of film production in those days. No wonder a roll of film is so expensive these days.

cliveh · Dec 2, 2023

Vaughn said:
Sirus -- we used stop bath in the printing room. Only in the roll film developing room was stop bath not provided.

Why?

Stop Bath.. How important?

MattKing

Moderator

Philippe-Georges

MattKing

Moderator

Philippe-Georges

Anon Ymous

koraks

Moderator

Anon Ymous

JerseyDoug

john_s

RalphLambrecht

Philippe-Georges

Carnie Bob

Rolleiflexible

Vaughn

alanrockwood

Sirius Glass

Vaughn

Mick Fagan

Rolleiflexible

alanrockwood

GLS

Mick Fagan

Don_ih

john_s

cliveh

Stop Bath.. How important?

Moderator

Moderator

Moderator

Privacy & Transparency

Privacy & Transparency