Water or Stop Bath

[kirk_keyes]

Ron - Thanks again for posting some of your excellent and practical knowledge.

 

I too have issues with several things in A&T' Film Cookbook book, but I'll stay on topic!

 

I found Point 1 to be pretty hypothetical on A&T's part. Exactly, where is their proof? It's not like we are adding concentrated acetic acid to dry sodium carbonate or some other base. These are actually pretty dilute solutions we are working with.

 

I do know that stirring water baths will most certainly raise the temperature of the bath - just try some bomb calorimetry to measure the heat of combustion of something and you will see that the water bath used increases in temperature. But it is on the order of less than a few tenths of a degree Celsius over ten or 15 minutes. And it certainly must be accounted for in this test where temperatures are measured to 0.001C. But for film processing, I'm sure it's a non-issue. How precisely do people control the temps of their chemicals - certainly not to a level where this kind of affect can be seen.

 

Point 2 - if I was processing in a dip and dunk several feet deep I might be more concerned about this, but with a hand tank or Jobo, I've never seen this. I've seen airbells when I started in photography, but never pin holes. And as you point out, I've found modern films to be pretty resistant to reticulation. I've yet to see it on my films.

 

If you keep your stop bath above pH 4.5 or so, you will not get much gaseous CO2 forming in carbonate solutions anyway. And for developers that use non-carbonate compounds to raise pH, it is a non-issue there.

 

Point #3, as Chris' link above showed, the volume of the gelatin actually reaches a minimum at pH 4.8. So it's not so much that the gelatin "swells" as a result of the acid stop, but it shrinks. Follwing the acid stop with a standard Rapid Fix, which has a pH of around 5.5, will cause a very small amount of swelling to occur.

 

If we use A&T's recommendation, a running water rinse and then alkaline fix, we would be causing the film to shrink less than a pH 4-5 stop but it will shrink some as the water bath should take the pH of the film to around 7, but then causing it to swell back up more by using the alkaine fix which probably has a pH of around 8 or 9. At this pH level, then film has probably swelled back up to near it's original volume when the film was placed in the developer.

 

So what's best - 1) shrinking the film with a properly made stop and then using a weakly acidic rapid fix which will not change the volume of the film much, or 2) use a water rinse, which again causes the film to shrink, but not as much as the stop, and then swell the film back up with an alkaline fix?

 

And if we consider the change in volume from dry, unprocessed film, to wet during processing, and back down to dry again after processing, how much does this pH induced swelling/shrinking matter. I suspect not much. Ron, do you have any comments on this?

 

Perhaps A&T, of which Mr. T is the inventor of the most popular alkaline fix on the market, are making an issue out of nothing because they have something to sell? I don't know. I would certainly like to see thier proof in this issue, which is something their book woefully sidesteps.

[garrylewis747]

advise about stopbaths,developers, and processing procedures are a lot like Texas weather- if you don't like it, wait a while and it will change.

[john_finch]

I very much agree... water is not a stop bath and a stop bath is very useful if we use 'short'

developing times; because we need to stop development accurately. But with development

times in access of 10 minutes and, to take it to the extreme perhaps, sometimes having

development times running into hours, do we really need to stop the film so abruptly when

a couple of rinses will wash out the developer and stop the film, for all intense and

purposes, developing? Is using a stop bath, for reasonable development times of 10 plus

minutes something we do 'because we can'? When I process a film I'm washing out the

developer so it does not contaminate my fixer, not because I have to stop the film on the

button. I just factor in the very slight deveopment that continues, as I rinse the film, and

get perfect results every time. How do I factor it in? By doing it the same every time.

[john_shriver]

So, Ron, for a simple stop bath made from 28% acetic acid and water, what ratio would you recommend?

 

Also, is it worth using distilled water, or is tap water OK. I have good water, but no filter. I suppose distilled water at least removes a source of dust.

[jay_de_fehr]

Lowell, as others have noted, the difference in using an acid stop bath and a water bath are very small in most cases, and important in only the most precise work. In the interest of precision, you wrote "The purpose of stop bath is to change the pH which halts development in the emulsion". Change the Ph of what? The developer saturated in the film? Are you suggesting that the developer solution saturated in the film is the same Ph as plain water, or that replacing the developer with plain water doesn't affect the Ph of the developer saturated in the film? Or does a plain water bath also change the Ph, and thereby stop the progress of development? If so, doesn't that make it a stop bath? A bath that stops development? The relative merits of an acid stop bath or a plain water rinse are very small, mostly insignificant, and do not warrant the use of absolute statements like yours. If you hope to encourage others to work with precision, you should write with precision as well.

[rowland_mowrey]

I'll try to answer all of you in one post, but if I miss anything, let me know.

 

1. I was unclear about distilled water. I am not against distilled water. I just meant that distilled water alone vs tap water alone will show a difference in swell of gelatin. The distilled water causes more swell, as the salts in tap water tend to repress swell. This varies with water hardness and the type of salts in your tap water. If you use distilled water to mix your chemistry, the added salts cause this difference to vanish. Moral: Don't use distilled water to rinse or wash your film or paper though! You could cause excessive swell.

 

2. I don't have any preference regarding fix, whether alkaline or acidic. I use what I have at hand. Color products require neutral fix and not alkaline or acid. B&W products can use either. As noted above, an acid pH tends to reduce swell somewhat. I have no evidence as to whether either pH is good or bad for B&W, but do have some for color products. Ammonium based fixes, regardless of pH fix about 2X faster than Sodium based fixes.

 

Finally; how did I come by this experience. Some want to have evidence. Ok, here is as much as I can describe for you. I used a device called a swellometer that measures the swell of a photographic material in microns vs time. The gelatin thickness is measured at the start and then each solution to test is placed on the material(s) and swell vs time is measured.

 

For hardness, an abrasive device is used to scrape the gelatin surface when dry and wet with each solution to measure the g/cm sq that causes abrasion by a graded sandpaper like device.

 

For pH, a surface electrode is used to measure the internal pH of the emulsion during this treatment.

 

Duplicate experiments are run for each test to get an averaged result and find out your 'precision' and 'accuracy'.

 

As for the heat during reaction, development is a redox reaction that generates acid. The reactions involved generate a miniscule amount of heat. The stop bath is an acid base neutralization that also generates a miniscule amount of heat. I'm trying to point out that heat is generated during development, stopping, and even fixing. Almost all chemical reactions generate heat. One exception is the dissolution of hypo in water. This absorbs heat.

 

AFAIK, there is absolutely no evidence that shows that heat generated by any reactions during photographic processing causes image degradation.

 

The chemicals involved in development are much larger in size than the hydrogen ion which is the active part of a stop bath. Therefore, since the neutralization of development by the stop bath involves the movement (diffusion) of these molecules a stop bath is faster by several orders of magnitude than the neutralization of development by water immersion. In one case, hydrogen ions diffuse inward rapidly, but in the other, huge organic molecules must diffuse outward through gelatin. Hydroxide, sulfite, and carbonate or borate must also move out of the film. Therefore, a stop is several orders of magnitude faster than a rinse in water for shutting off development. It is also more uniform due to the small size of the hydrogen ion.

 

My preferred stop bath is 20 ml/l of glacial acetic acid (~2%) or 10 ml/l of glacial acetic acid (~1%). This is only approximate due to the density of the acid not being 1.00000. I mix it in 5 liter batches of 100 ml of acid in 5 liters. Then if I want 1%, I dilute 1:1 with water. I buy glacial acetic acid in a gallon jug from EK for about $23. It lasts me several years. (In fact, that price is probably low as my current bottle is so old, and it is still half full).

 

I may comment further on some things in A&T if there is any interest. (seems that there is!)

 

Ron Mowrey

[john_stockdale2]

Water is not a stop bath, but is likely to be inadequate if:

 

1. It is too brief, and

 

2. The developer is strong, for example the graphic arts process described above, or if the dev time is quite short (Neopan in Microphen)

 

I think that sometimes we are just lucky that what we do works as a result of factors that we have not considered, such as water supply, or choice of certain materials.

 

I don't use acid stop, but why it works I don't fully understand. Most of my developers are either very dilute, or in the case of fast acting Microphen, it's not very alkaline.

 

If water stop is making your fixer deteriorate faster, then it is inadequate.

[rowland_mowrey]

More comments about gelatin.

 

For those of you interested, there are three types used in photographic products. There is bone gelatin discussed here: 'www.screensound.gov.au' as referenced above. This has its minimum swell at its isoelectric point of 4.8. Then there is pig gelatin which has an isoelectric point of around 9. The final type is either bone or pig gel modified by reaction with organic materials to modify the structure of the gelatin for better photographic properties. I cannot discuss this latter type of gelatin for obvious reasons.

 

There are also polymers that are added to gelatin to change their properties. I cannot discuss those either.

 

All of these ingredients determine the final physical properties of the photographic products you use. I can say that most major companies seem to use bone gel and therefore, the data presented at the reference above appears to be representative of what you will find with your materials from EK, Fuji, Agfa, Konica and Ilford.

 

Use of pig gel, for example, will result in a product that differs substantially from the norm that you usually see, and will resemble a film from the 40s or so (hint, hint). It will swell differently, and will harden differently.

 

But, it should be remembered that a stop bath will not adversely affect any of these products either. A stop bath is a non-problem.

 

Oh, if the odor bothers you, use citric acid stop then. If the cost bothers you, you probably can't afford to be in conventional photography in the first place. Stop baths represent such a miniscule part of the cost, I really can't believe that anyone would remark on this.

 

In testing photographic products in R&D or for quality control during manufacturing, a stop bath is a must in all B&W processes for accurate process control! I can state categorically that without a stop bath, the results would not be consistant enough for the demanding needs of quality control. I hasten to add that an acid stop-fix is suitable, but will exhaust rapidly unless replenished. In color processes, the situation is slightly different, but a stop bath is essential in the RA process at least, to prevent streaking of prints. Also, in color, silver development can be allowed to continue, as long as dye formation is stopped. (consider that for a bit if you will, and the implications inherent in it)

 

Regards.

 

Ron Mowrey

[al_divenuti]

>>Actually, development itself generates heat in the emulsions of film and paper both, and the pH drops considerably during the development process. In some developers, the pH in high silver areas is quite low, in fact, acidic in some cases.

 

I have heard of development taking place at temperatures up to over 120 deg C without severe reticulation or clumping in a dry process, and up to 120 deg F in wet processes without clumping. I've done it in fact.

 

I'm sure that these assertions are both true but if the grain clumping mechanism is sensitive to thermal gradients rather than absolute temperature than it's still possible that rapid changes in PH induce sever thermal gradients during the stop that would cause grain clumping while the (I would expect) less abrupt changes in PH during normal development are safe. And still allows for high temperature free of reticulation.

 

The above, admittedly, is a rationalization of the A&T stance and I don't have any empirical data to prove it.

 

The problem with A&T's Film Developing Cookbook is that many of these observations are owed to researchers (Zawadski, Crawley, Haist) whose work (if not the conclusions in the work) are still the intellectual property of various entities. So while the results of their research may be freely shared with A&T, details of the research may not.

[al_divenuti]

>>Acid fixers don't need a stop because they are "stop-fixes" by definition. Many people prefer to use them anyway.

 

Lowell...I think you'd be hard-pressed to find anyone who prefers an acid fix these days. REAL hard-pressed as a matter of fact given:

 

1) Alkaline fixer is a lot easier to wash out of negs or paper...

2) It's possible to overfix using an acid fixer

 

And for those of us using staining developers acid fixers are simply out of the question altogether since they reduce image stain.

[rowland_mowrey]

Al;

 

Sorry, but the only comment you made that I can agree with is the one about staining developers! Even there, the evidence against acid fixes and stops is weak, but I would tend to believe it until proved otherwise.

 

The heats of reaction for development and for acid-base neutralization are not sufficient for the effect you and A&T postulate. If it did exist, it would be front page news in the photographic journals.

 

Since it would be possible to formulate around this supposed problem, it would probably be a patentable item, or at the least a major publication in the SPSE Journal or someplace similar. I have never heard of either.

 

Grant never mentioned anything like that to me, nor in any of his publications either AFAIK. I have never heard of it internally at EK either.

 

The bottom line is this. Development continues in post development water rinses. Whether it is a problem to you or others is debatable, but a difference can be proven to exist. I have done it. More than once. In fact, patents and publications exist to show that rinses after development can be used for further milder development with advantages to image structure. Konica used post development wash for their color negative film to improve image structure and dye hue. Edge effects were enhanced by this process, not worsened.

 

I could go on and on, but I have enough evidence to prove it satisfactorily to myself, and have proven it and seen it proven during the course of development and testing of photographic products.

 

Ron Mowrey

[rowland_mowrey]

Al;

 

One last fact that I forgot to address. Alkaline fixes may indeed wash out faster from film and paper, but it is probably due to the fact that the gelatin is more swollen (as per the URL above) when the pH is high.

 

The result may be more rapid washing at the expense of tender swollen gelatin in your film and paper. IDK for sure, but without evidence either way, I would be cautious.

 

And, if you remember, EK made an alkaline hardener fix years ago. It wasn't very fast IIRC. So hardening in an alkaline fix is not necessarily the solution. In addition, ammonium based alkaline fixes have a very strong odor, which is far worse than the vinegar odor of stop baths, and the sulfite odor of fixes. Sodium based alkaline fixes are not very fast.

 

In addition, you must be careful about the formation of Silver Hydroxide in your coating if the pH goes too high. If that happens, you may have a real problem.

 

I hope that this has given you some things to think about.

 

Ron Mowrey

[patrick_gainer]

Kirk,

 

Hydrogen bromide is an acidic bromide. Dehydroascorbic acid is more acidic than ascorbic acid. The alkali metal salts of dehydroascorbic acid are more acidic than the corresponding salt of ascorbic acid. Whichever way you want to say it is OK by me.

 

When bromine ions are set free as part of the reduction of silver bromide, two of them combine with one molecule of an ascorbate salt to form 2 HBr molucules and one molecule of the dehydroascorbic salt. Does this sound better? The net result is lower pH in the areas of higher activity which of course results in some self limiting. I think this means the the edge effects of ascorbate developers will be on one side of the edge while those of hydroquinone will be on the other.

 

I forgot why I got off on this tangent.

[kirk_keyes]

"When bromine ions are set free as part of the reduction of silver bromide, two of them combine with one molecule of an ascorbate salt to form 2 HBr molucules and one molecule of the dehydroascorbic salt. Does this sound better?"

 

Patrick, yes, that sounds better - although components in ionic solutions can't really be said to have combined. But yes, thanks for the clarification.

[kirk_keyes]

Al wrote, "And for those of us using staining developers acid fixers are simply out of the question altogether since they reduce image stain."

 

Al, can you point me to some tests where this has been demonstrated? I have compared stain levels in PMK processed film processed as best to identical as I can using a water bath and a stop bath and I have found the water bath gave slightly higher density than the stop bath - for both stain and silver density. It was such a small difference that I attribute the results to the stop having halted development much faster than the water rinses, as it should have.

 

My stop was much more acidic than any rapid fix so I'm at a loss as to where an alkaline fix would preserve more stain than a rapid fix.

 

Have you done any tests in this regard?

[garrylewis747]

I'm with Kirk. Has anybody acually done side-by-side comparison tests

with any staining developer as to;

acid/water stopbath effects on the stained images or

acid/alkaline fixer effects on stained image?

[patrick_gainer]

Ron said:

"In addition,

ammonium based alkaline fixes have a very strong odor, which is far worse than the

vinegar odor of stop baths, and the sulfite odor of fixes. "

 

I have had open 16 X 20 trays of TF4 diluted 1+3 in my very small darkroom without that strong odor. OTH, it is also not true that alkaline fixers do not bleach. They will, given enough overtime.

[garrylewis747]

>OTH, it is also not true that alkaline fixers do not bleach. They >will, given enough overtime.

 

Given enough time and weak dilution, Acetic Acid will bleach. Use to

use 28% (straight form the cubetainer) to "clean" silver from old developer trays- outdoors of course.

[rowland_mowrey]

Patrick;

 

If you have an alkaline ammonium thiosulfate fix, then you cannot avoid having an ammonia odor. The vapor pressure of ammonia over the tray would be quite considerable. Probably the concentration of ammonia over the tray would be higher than sulfite over a tray of acid fix just due to concentration alone. (~10 g/l of sulfite salts vs ~100 g/l thiosulfate salts)

 

So, either the pH is more like 6.5 or so (ie, not alkaline), or the fix is not ammonium based which slows it down considerably. Even at pH 6 - 7 there is some ammonia odor in an ammonia based fix. This is especially true if no stop is used.

 

I have never expressed an opinion on bleaching of silver images by hypo, but have stated my opinion above about washing rate when using one of the alkaline fixes.

 

Art, others;

 

As far as heat generated by stop baths, I have given more thought to it, and I guess Kirk would probably have more concrete information, but here is my opinion. Due to the energy of the development reaction, more heat would be liberated during development than during stopping. In any case, this heat is very tiny, but measurable by a calorimeter.

 

Therefore if (I emphasize IF) any effects on image structure are caused by heat, it is more likely to take place in the developer when there is more heat generated, and the gelatin is more swollen, and there are more solvents present to influence any clumping. If anything, the stop bath would probably tend to quench clumping if any were to be taking place. That is my opinion.

 

I think Kirk's observation above about higher D-min (fog) when using a wash instead of a stop bath is important to note here. This is not uncommon and supports all of my experiments.

 

I would like to add that clumping would tend to lower micro contrast. This is contrary to other posts and some printed statements that I have seen.

 

It does that by smearing out the image of the finer lines such as 1 and 10 micron, thereby lowering the density of such lines (yes, the density is lower, as the majority of the 'clump' will come, in part, from the center or peak of the line). It would therefore decrease sharpness of these fine lines. My reference is Mees "The Theory of the Photographic Process".

 

Ron Mowrey

[kirk_keyes]

Ron - it's not in the Dmin of the film that I saw a difference between stop bathed and water bathed film - it was in the higher densities. Which is where I would expect to see a difference. And the difference was small - around 0.03-0.04 OD if I remember correctly. Not a big difference.

 

So again I ask, has any one else actually done a test to compare water bath vs. stop bath, or even acid fix vs. alkaline fix?

[rowland_mowrey]

Sorry Kirk, I guess I misunderstood your answer. When you said stain was higher, I took that as D-min.

 

Ron Mowrey

[al_divenuti]

Ron,

 

Thanks for the response to my last post. I admit, my postulation was a stretch. Odd that this should be found in that book without apparent justification.

 

For what it's worth A&T do not summarily dismiss Acid Stop Baths in the Darkroom Cookbook - they simply say to avoid those that produce CO2 gas during upon contact with Carbonates. They cite Kodak SB-1 as an acid stop bath that should not cause pinholes.

 

But I have to hold my ground on Acid Stop Baths and pinholes because I've heard too many second-hand storie from folks.

[rowland_mowrey]

Al;

 

I can agree with your comment. I too have heard lots of 'second hand' stories, but when checked out, none have any foundation other than possible air bells in the developer or anecdotal evidence.

 

I have articles going back to 1941 which support the use of stop baths even with the softer films of that era, and refuting the issues against stop baths brought up here.

 

As others here point out, no one has been able to generate pinholes or has ever seen or gotten them 'first hand'. That is the problem Al. You see, with myth busting you have to see it first hand. I have been using stop baths and doing research on stops, fixes, bleaches, blixes, developers, films and etc for about 50 years and 32 of them at EK, and have only heard that one reference. I have never seen it or heard of the problem otherwise.

 

You see the problem. I have tried to make it happen. It can happen actually, but under conditions that are preposterous for a commercially viable photographic system. I made it happen under these conditions:

 

1. Unhardened photographic material.

 

2. Unsubbed material (no adhesive layer/material) to make gelatin stick to support.

 

With that case and 50 g/l of carbonate and 2% acetic acid at temperatures above 75 degrees (this was run using C-22 and P-122 type chemistry with temperature variations), I was able to generate pinholes and actually blow the gelatin off the support. Now, you have to admit that that is kind of extreme! No such material would ever be sold. That is how hard I had to try, to generate pin holes with a stop bath, so I have first hand experience with those conditions necessary to create the problems cited by A&T, and find that they are impossible to create outside of a lab, and only with non-viable photographic materials.

 

The problem is, that even my experiment is weak, as my supervisor at the time pointed out, the temperature where the pinholes and 'blowoff' took place was nearing the melting point of gelatin and therefore the experiment only showed that gelatin could be forced to leave the support by CO2 if near its melting point, and not just by the force of the CO2 gas bubbles. So, I only proved that this could take place near the melting point of unhardened gelatin on a non-adhesive support, otherwise I could not make it take place. Therefore, the conclusion was that it could not happen in the 'real world'.

 

I have run dozens of experiments to try to prove/disprove this. It will not happen. I rest my case.

 

Ron Mowrey

[patrick_gainer]

Ron, you said:

"So, either the pH is more like 6.5 or so (ie, not alkaline), or the fix is not ammonium

based which slows it down considerably. Even at pH 6 - 7 there is some ammonia odor

in an ammonia based fix. This is especially true if no stop is used. "

 

TF4 is definitely ammoniacal. I didn't say there was absolutely no odor, but that it is not a strong odor. TF4 concentrate is actually what you might call a slurry. At 1+3 dilution, it is still very strong, clearing film in about 30 seconds when freshly mixed. I have not measured pH, but am taking the word of Photographer's Formulary that it is alkaline. It certainly causes no effervescence when mixed with carbonate developers.

 

It appears that you are not reporting observed behavior of TF4, but are stating theories. Isn't that what you advised someone else against?

[bill_troop1]

Yes, Mr. Mowerey, I wish you would actually

try my product before spouting off about it

all over the Internet. At last I know how

Mssrs Bush and Kerry must feel, first hand,

thanks to you!

 

The information and technology I have published

with regard to alkaline fixers comes straight

from Grant Haist (still alive) and H.D. Russell,

whom Grant considered Kodak's greatest practical

engineer. That goes for the glutaraldehyde/succinaldehyde

stuff as well, all of which Russell used in the X-o-mat

process, but I guess you don't know anything about that.

 

Please, if anybody ever did his homework, I did. That

should be obvious. And it should also be obvious that

I gave as much detail and sourcing as I could without

compromising my informants.

 

Why don't you at least try to check your facts

before you criticize me? Or have the courtesy

to bring these issues to my attention? I would

never have heard of this except by the sheerest

accident of someone telling me about this thread.

 

What I find particularly galling is that you

are posing as an expert from Kodak. Maybe

you are. But you're not an expert in what

you're talking about here, and you don't

have the experience of having discussed these

particular issues over a 25-year period with scientists

of the stature of Haist, Russell, James, and Henn,

or for that matter, Zawadzki and Dickerson

 

You know, in all the years that I have had my

relationships with the top people at Kodak,

nobody ever told me, 'oh, go to Mowerey - he

really knows something special about this.'

Are you really in that class? If so, I'd like

to get to know better!

 

I talked to the people who _did_ know something

special about this. I spent 20 years doing that

before I published my book. I think I have the

right to resent someone coming in and saying,

oh, no, that's all crap. And this, without even

the courtesy of letting me know that

he's doing it.

 

There isn't a syllable in FDC I am ashamed of

or would change now. I worked very hard, for

many years to get the best information I could,

out to the photographic community. I am damned

proud of that work. Now you accuse me of making

it up. But that book was read, over and over again,

by Haist, by James, by Dickerson and Zawadzki,

by Crawley. I don't see how I could have done

a better job. - Bill Troop