Stop Bath.. How important?

[JBrunner]

Thank you. Yes, and if I recall your opinion is that water works just fine. I don't know about prints, but for film I am 99.99% sure that this is true.

I think it is a very telling fact that no one with a contrary opinion has shown any experimental data showing that for processing of negatives water is in any way inferior to acid stop bath, regardless of whether it is their own experiments or experiments reported by someone else. (I am referring to the quality and properties of the negatives here.)

The one caveat is that in making the comparison between an acid stop bath and water one might need to shorten the development time by a few seconds if using water as a stop bath to compensate for the fact that an acid stop bath arrests development a tiny bit faster than a water stop bath, but even if one didn't use an adjusted development time I'll bet anyone would be hard-pressed to detect a difference.

By the way, did you used to live in Utah?

I did. I'm still around there frequently..S a matter of fact I'm headed there in a week or so to do a shoot in Moab for a commercial client.

 

[Tom Kershaw]

shoot in Moab for a commercial client

Are you using the Pentax 645Z for commercial work?

 

[foc]

We could use two of the same film brands, same speed, same batch.
We could set up the studio to shoot test shots under controlled lighting.
We could use the same camera with the same lens for the exposures
We could develop both films in the same developing tank, for the same time as recommended by the manufacturer, at the same temperature.
We could use stopbath with indicator for one film and water stop for the other for the same recommended time
We could fix both films for the same time, as recommended.
We could wash both films as recommended and dry them side by side.
We could examine the negatives and do densitometer readings and log our findings.
BUT
Maybe life is too short.

 

[JBrunner]

Are you using the Pentax 645Z for commercial work?

I am. Does a good job the way I use it.

 

[Tom Kershaw]

I am. Does a good job the way I use it.

I'm sure it does, just that I remember you saying a while ago you might change the Pentax for something else.

 

[Sirius Glass]

We could use two of the same film brands, same speed, same batch.
We could set up the studio to shoot test shots under controlled lighting.
We could use the same camera with the same lens for the exposures
We could develop both films in the same developing tank, for the same time as recommended by the manufacturer, at the same temperature.
We could use stopbath with indicator for one film and water stop for the other for the same recommended time
We could fix both films for the same time, as recommended.
We could wash both films as recommended and dry them side by side.
We could examine the negatives and do densitometer readings and log our findings.
BUT
Maybe life is too short.

Except the densitometer does not measure the areas that continued to develop longer than the rest of the film since stop bath was not used. As stated your "experiment" would not prove anything about stop bath.

 

[Michel Hardy-Vallée]

One thing stop bath surely cannot stop is this runaway thread!

 

[cliveh]

It doesn't? Why?

If you are using an alkali developer, then large throughput into a water bath will render that water alkali. If you then transfer prints to an acidic fixer, the alkali content will degrade the acidic pH of the fixer.

 

[MattKing]

As I understand it, developer residue itself also impedes the longevity of the fixer.
I'll let the chemists here either correct me, or explain why.

 

[JBrunner]

Personally, I favor f/11 as a stop.

 

[cliveh]

Personally, I favor f/11 as a stop.

I prefer f/8

 

[alanrockwood]

That’s crazy talk.

Crazy talk for sure. Doesn't everyone one know that f/5.6 is going to give the sharpest photos when using a normal prime lens on a 35mm camera.

 

[alanrockwood]

As I understand it, developer residue itself also impedes the longevity of the fixer.
I'll let the chemists here either correct me, or explain why.

Possibly developer residue may reduce the longevity of the fixer. However, from simple chemical reasoning, acidifying the film is not likely to result in faster removal of developer from the film, so it's not likely to much affect the amount of carryover into the fixer.

It's actually not quite this simple, but acidifying the film in the stop bath will convert the developer from a negative ion to a neutral molecule or maybe even a positive ion, depending on the chemical structure of the developer and the pH of the stop bath. It does not destroy the developer, and changing it from negatively charged molecules to neutral will not likely change the diffusion coefficient very much, so the developer (in the neutral form) is not likely to diffuse out into the stop bath solution much if any faster or slower than if it were in the negatively charged form. Hence, about the same amount of developer will remain in the film, regardless of whether the stop bath was at a low pH or neutral pH. Consequently, about the same amount of developer will later diffuse into the fixing bath, regardless of whether the stop bath was acidic or neutral.

After that long-winded explanation, let me add that what I wrote above is still a simplification, possibly and over-simplification, and here's why. The time it takes for the developer molecules to diffuse out of the emulsion is probably not the same as diffusion through an aqueous solution, and here's why. The residual developer, may have some affinity (in the chemical sense) for gelatin molecules. There are dispersion forces, dipole/dipole force, ion dipole forces, and ion-ion forces that may be present between the gelatin molecules and the residual developer molecules. If so, then the developer molecules may have a tendency to be sticky relative to the gelatin molecules, and the amount of this stickiness will depend on what forces are predominating, and this is going to depend a lot on whether the developer is in ionic form or neutral form. It also depends on the acid/base chemistry of the gelatin. For example, if the developer is in neutral form, and if the pH is at the isoelectric point of the gelatin then the developer molecules are going to avoid interacting with water (which is highly polar) and will tend to stick to the gelatin. Other conditions may tend to produce different results. Hence, the diffusion rate of the developer out of the emulsion may depend on many factors that are hard to predict without additional information.

In any case, the amount of residual developer left in the emulsion has to be pretty low, and if any development occurs after the emulsion is put in the stop bath, it will tend to favor the chemical depletion of the developer more in the water stop bath than in the acid stop bath, so if anything there is likely to be less developer to transfer to the fixing solution if water is used as the stop bath than if an acidic stop bath is used, and to that extent a low carryover to the fixing solution is probably favoring a water stop. However, in any case, the amount of residual developer left in the emulsion is probably so low that it can be pretty much ignored. This is because the volume of the emulsion is a tiny fraction of the volume in the development tank, and much of the emulsion volume is taken up by gelatin molecules, which would not leave much volume left to hold the developer in the emulsion. This thought may need to be modified a bit if there is a high affinity between gelatin molecules and developer molecules, but even in this case it's hard to imagine that there is much residual developer left in the emulsion. If it is perceived as a problem then two successive "water stops" on the film would eliminate this as a concern.

Also, if one is using a water stop then a lot of the concerns that have been raised here about buildup of developer in the stop bath are eliminated by simply by not trying to re-use the water. Just use it as a stop bath in one-shot, and then discard. Water is pretty cheap where I live (less than $4 for 1000 gallons), so the cost of tossing the water after each use is negligible.

The above discussion is based on general chemical considerations, rather than a special expertise in photochemical chemistry, but if there are parts of the analysis that are wrong then they can certainly be discussed.

My credentials: PhD in Chemistry, specializing in physical chemistry. The final 16 years of my career were in clinical chemistry, which by the way is the same field where Richard Henry (author of "Controls in Black and White Photography") spent his career. In fact, he was a major figure in the field of clinical chemistry.

 

[alanrockwood]

Possibly developer residue may reduce the longevity of the fixer. However, from simple chemical reasoning, acidifying the film is not likely to result in faster removal of developer from the film, so it's not likely to much affect the amount of carryover into the fixer.

It's actually not quite this simple, but acidifying the film in the stop bath will convert the developer from a negative ion to a neutral molecule or maybe even a positive ion, depending on the chemical structure of the developer and the pH of the stop bath. It does not destroy the developer, and changing it from negatively charged molecules to neutral will not likely change the diffusion coefficient very much, so the developer (in the neutral form) is not likely to diffuse out into the stop bath solution much if any faster or slower than if it were in the negatively charged form. Hence, about the same amount of developer will remain in the film, regardless of whether the stop bath was at a low pH or neutral pH. Consequently, about the same amount of developer will later diffuse into the fixing bath, regardless of whether the stop bath was acidic or neutral.

After that long-winded explanation, let me add that what I wrote above is still a simplification, possibly and over-simplification, and here's why. The time it takes for the developer molecules to diffuse out of the emulsion is probably not the same as diffusion through an aqueous solution, and here's why. The residual developer, may have some affinity (in the chemical sense) for gelatin molecules. There are dispersion forces, dipole/dipole force, ion dipole forces, and ion-ion forces that may be present between the gelatin molecules and the residual developer molecules. If so, then the developer molecules may have a tendency to be sticky relative to the gelatin molecules, and the amount of this stickiness will depend on what forces are predominating, and this is going to depend a lot on whether the developer is in ionic form or neutral form. It also depends on the acid/base chemistry of the gelatin. For example, if the developer is in neutral form, and if the pH is at the isoelectric point of the gelatin then the developer molecules are going to avoid interacting with water (which is highly polar) and will tend to stick to the gelatin. Other conditions may tend to produce different results. Hence, the diffusion rate of the developer out of the emulsion may depend on many factors that are hard to predict without additional information.

In any case, the amount of residual developer left in the emulsion has to be pretty low, and if any development occurs after the emulsion is put in the stop bath, it will tend to favor the chemical depletion of the developer more in the water stop bath than in the acid stop bath, so if anything there is likely to be less developer to transfer to the fixing solution if water is used as the stop bath than if an acidic stop bath is used, and to that extent a low carryover to the fixing solution is probably favoring a water stop. However, in any case, the amount of residual developer left in the emulsion is probably so low that it can be pretty much ignored. This is because the volume of the emulsion is a tiny fraction of the volume in the development tank, and much of the emulsion volume is taken up by gelatin molecules, which would not leave much volume left to hold the developer in the emulsion. This thought may need to be modified a bit if there is a high affinity between gelatin molecules and developer molecules, but even in this case it's hard to imagine that there is much residual developer left in the emulsion. If it is perceived as a problem then two successive "water stops" on the film would eliminate this as a concern.

Also, if one is using a water stop then a lot of the concerns that have been raised here about buildup of developer in the stop bath are eliminated by simply by not trying to re-use the water. Just use it as a stop bath in one-shot, and then discard. Water is pretty cheap where I live (less than $4 for 1000 gallons), so the cost of tossing the water after each use is negligible.

The above discussion is based on general chemical considerations, rather than a special expertise in photochemical chemistry, but if there are parts of the analysis that are wrong then they can certainly be discussed.

My credentials: PhD in Chemistry, specializing in physical chemistry. The final 16 years of my career were in clinical chemistry, which by the way is the same field where Richard Henry (author of "Controls in Black and White Photography") spent his career. In fact, he was a major figure in the field of clinical chemistry.

There is a way to get some kind of handle of the relative affinity between emulsion and developer. It is to make a chromatography column with shredded up film as the stationary phase. The mobile phase would be run a several different pH levels and the retention time of the developer would be compared under those different conditions. I won't take the trouble to discuss all of the nuances of this experiment, and I an not actually suggesting that anyone perform the experiment.

 

[cliveh]

Possibly developer residue may reduce the longevity of the fixer. However, from simple chemical reasoning, acidifying the film is not likely to result in faster removal of developer from the film, so it's not likely to much affect the amount of carryover into the fixer.

It's actually not quite this simple, but acidifying the film in the stop bath will convert the developer from a negative ion to a neutral molecule or maybe even a positive ion, depending on the chemical structure of the developer and the pH of the stop bath. It does not destroy the developer, and changing it from negatively charged molecules to neutral will not likely change the diffusion coefficient very much, so the developer (in the neutral form) is not likely to diffuse out into the stop bath solution much if any faster or slower than if it were in the negatively charged form. Hence, about the same amount of developer will remain in the film, regardless of whether the stop bath was at a low pH or neutral pH. Consequently, about the same amount of developer will later diffuse into the fixing bath, regardless of whether the stop bath was acidic or neutral.

After that long-winded explanation, let me add that what I wrote above is still a simplification, possibly and over-simplification, and here's why. The time it takes for the developer molecules to diffuse out of the emulsion is probably not the same as diffusion through an aqueous solution, and here's why. The residual developer, may have some affinity (in the chemical sense) for gelatin molecules. There are dispersion forces, dipole/dipole force, ion dipole forces, and ion-ion forces that may be present between the gelatin molecules and the residual developer molecules. If so, then the developer molecules may have a tendency to be sticky relative to the gelatin molecules, and the amount of this stickiness will depend on what forces are predominating, and this is going to depend a lot on whether the developer is in ionic form or neutral form. It also depends on the acid/base chemistry of the gelatin. For example, if the developer is in neutral form, and if the pH is at the isoelectric point of the gelatin then the developer molecules are going to avoid interacting with water (which is highly polar) and will tend to stick to the gelatin. Other conditions may tend to produce different results. Hence, the diffusion rate of the developer out of the emulsion may depend on many factors that are hard to predict without additional information.

In any case, the amount of residual developer left in the emulsion has to be pretty low, and if any development occurs after the emulsion is put in the stop bath, it will tend to favor the chemical depletion of the developer more in the water stop bath than in the acid stop bath, so if anything there is likely to be less developer to transfer to the fixing solution if water is used as the stop bath than if an acidic stop bath is used, and to that extent a low carryover to the fixing solution is probably favoring a water stop. However, in any case, the amount of residual developer left in the emulsion is probably so low that it can be pretty much ignored. This is because the volume of the emulsion is a tiny fraction of the volume in the development tank, and much of the emulsion volume is taken up by gelatin molecules, which would not leave much volume left to hold the developer in the emulsion. This thought may need to be modified a bit if there is a high affinity between gelatin molecules and developer molecules, but even in this case it's hard to imagine that there is much residual developer left in the emulsion. If it is perceived as a problem then two successive "water stops" on the film would eliminate this as a concern.

Also, if one is using a water stop then a lot of the concerns that have been raised here about buildup of developer in the stop bath are eliminated by simply by not trying to re-use the water. Just use it as a stop bath in one-shot, and then discard. Water is pretty cheap where I live (less than $4 for 1000 gallons), so the cost of tossing the water after each use is negligible.

The above discussion is based on general chemical considerations, rather than a special expertise in photochemical chemistry, but if there are parts of the analysis that are wrong then they can certainly be discussed.

My credentials: PhD in Chemistry, specializing in physical chemistry. The final 16 years of my career were in clinical chemistry, which by the way is the same field where Richard Henry (author of "Controls in Black and White Photography") spent his career. In fact, he was a major figure in the field of clinical chemistry.

In your explanation, have you taken any account of throughput? If a single person is producing say 10 prints in one hour you maybe correct, but how does your explanation equate to 25 students through putting 200 prints in the same period, re water or acidic stop bath?

 

[CMoore]

Who said stop bath is useless? I use it all the time. You have a strange habit of not actually reading anything people write prior to responding. Either that or you have a serious reading comprehension problem. Or perhaps English isn’t your first language.

I use it for paper, but not usually for film, just a quick flush with water. Besides, doesn't the Fix stop development.?
Yeah, i did not read that anybody was saying it was "Useless".
But maybe somebody did somewhere, this is a long thread.

 

[JBrunner]

Crazy talk for sure. Doesn't everyone one know that f/5.6 is going to give the sharpest photos when using a normal prime lens on a 35mm camera.

35mm? Wassat?

 

[alanrockwood]

35mm? Wassat?

I dunno, lunatic fringe maybe?

 

[alanrockwood]

In your explanation, have you taken any account of throughput? If a single person is producing say 10 prints in one hour you maybe correct, but how does your explanation equate to 25 students through putting 200 prints in the same period, re water or acidic stop bath?

My explanation does not address throughput.

 

[Vaughn]

In your explanation, have you taken any account of throughput? If a single person is producing say 10 prints in one hour you maybe correct, but how does your explanation equate to 25 students through putting 200 prints in the same period, re water or acidic stop bath?

Those are rather insane moments (although we only had 19 enlargers/stations), usually before critiques for the beginning classes. My assistants and I tried to keep on top of the chemicals, changing the developer and trying not to screw someone up who was about to nail their print with the old developer, constantly testing the fixing baths, trying to keep prints moving and not stalling in the fixer. A mad house and I did not lose sleep if someone's print stained into oblivion...they should know better and could print it again when there was just three of four people in the dark. That is why I maintained up to 80 hours of open darkroom hours a week.

 

[Sirius Glass]

I use it for paper, but not usually for film, just a quick flush with water. Besides, doesn't the Fix stop development.?
Yeah, i did not read that anybody was saying it was "Useless".
But maybe somebody did somewhere, this is a long thread.

Stop bath is most critical for film. For prints sometimes water is used so that one can do localized development. But then you have me blocked so you will never read this.

 

[Sirius Glass]

In your explanation, have you taken any account of throughput? If a single person is producing say 10 prints in one hour you maybe correct, but how does your explanation equate to 25 students through putting 200 prints in the same period, re water or acidic stop bath?

That is exactly when using stop bath with indicator is most important. Everyone knows when the stop bath needed to be replaces and than keeps the hypo [yes that is the correct term used correctly] from being polluted.

 

[CMoore]

. But then you have me blocked so you will never read this.

????????

 

[Sirius Glass]

????????

Well what a surprise. I will drink to that, but I am not drinking stop bath.

 

[CMoore]

Well what a surprise. I will drink to that, but I am not drinking stop bath.

Right or wrong, i just run water through the development tank and then poor in the fix. Might be a bit of a waste of water, but i do not develop that much film. Seems to work fine with Ilford, or is it Ilfotec 110....... and HP5 or FP4

No doubt the "Correct Method" is to use a "Real" stop bath. Whatever.

For paper, i use Citric Acid and change it at least every day, some times twice. Its cheap and easy.......

Anybody know how "Exhausted" the indicator fix is when it starts to turn Black/Gray.?