Stop Bath.. How important?

RA4 colour negative print chemistry, is 45 seconds in the developer bath, then 45 seconds in the bleach/fix bath.

Or 45 seconds in the developer bath, 15 seconds in a stop bath 15 seconds in a wash bath, 75 seconds in a bleach bath, 45 seconds in a wash bath, 45 seconds in a fixer bath, 90 seconds in a wash bath. This was one system Fuji had in Australia, we thought of emulating it to save on chemistry and to effectively allow the chemistry to last 6 months with replenishment. Certainly cost effective, apparently the stop bath into the bleach was the real cost saver as bleach then lasted forever.

Whichever way you process RA4, 45 seconds in the developer bath at 38C is about the shortest standard process in the business.

Mick.

Photo Engineer said:

Well, very well done Alan. OTOMH I can add that the diffusion rate of a proton is orders of magnitude more rapid than any inward or outward diffusion of chemistry such as Metol, HQ, Phenidone and etc. I can add that wetting of the surface of the film, even if wet already with developer, is a function of agitation and thus, size does matter! A large print or film (say 4x5 or larger) may suffer from this.

Also, the shorter the development time, the more critical stopping becomes.

PE

Click to expand...

What Ron said!!

"... also, the shorter the development time, ... "

I occasionally invest a lot of time and effort into making what I hope are good images. When it comes time to turn my idea into metallic silver suspended in (Ron, help me here) gelatin or whatever, I am quite anxious that I have complete control over my development process. Silly mistakes such as not accounting for the ~15 seconds of additional development because the ph of my tap water was insufficient (thanks, Alan Rockwood) to neutralize the alkaline of my developer...

I love learning stuff and never stop getting excited about hearing from people who know more than I do.

alanrockwood said:

The final conclusion I make is that it doesn't matter if one uses pure water or stop bath, provided one makes a slight adjustment to the nominal development time to account for the difference between acid stop bath and pure water.

Click to expand...

Alan, I am not trying to be facetious here and certainly respect your undying dedication to the arts and methods and theories of both chemistry and physics, but, in the end, in the very end, is not my original idea the most pragmatic, simply because it covers all bases and leaves absolutely nothing to chance? My method requires no developer time adjustment, is absolute, and carries no caveats threatening image destruction.

What I again propose is to reap the benefits of the stop bath's acid impetus, but use it strictly as a one-shot format in an extremely dilute mixture. Alan, even your highly educated and theoretical mind has to agree that my proposal solves both dilemmas: that of 1) stopping development in its very tracks and 2) strictly, and with absolute totality, avoiding the mere possibility of pinholes from manifesting. 'One-shot' guarantees ongoing potency and extreme dilution guarantees absence of harm. Sometimes common sense ascends into the same lofty category as does academic excellence (with its necessarily theoretical underpinning).

My solution 'for the solution' is as follows: employ any of the following to make one liter of the David Lyga 'one-shot' stop bath: 2.5 mL glacial acetic acid, or 3 mL Kodak Indicator Stop Bath concentrate, or 9 mL 28% acetic acid, or 50 mL white vinegar (5% hops). Thus, perhaps I have just contributed towards the assassination of this thread, which has encouraged a wasteful proliferation of keystrokes.

Indeed, we need not always hinge our lives upon the absolutes (i.e., "to use it or not"). Instead, a hybrid solution to a problem can be the very road to take. We know that acid stops development but too much causes potential problems. Let us go from there and formulate a practical solution for this dilemma, (since we have two 'goods' which, however, also contain two 'bads'). A synergy of the 'goods' can be held intact while negating the 'bads'. - David Lyga

I love acid stop baths because I know the thing goes right in and kills the damn mofo developer right away.

Bam shazam. No waiting, no soft manners, no maybes, no what ifs.

Pour in, kill it, pour out, sniff it.

David Lyga said:

My solution 'for the solution' is as follows: employ any of the following to make one liter of the David Lyga 'one-shot' stop bath: 2.5 mL glacial acetic acid, or 3 mL Kodak Indicator Stop Bath concentrate, or 9 mL 28% acetic acid, or 50 mL white vinegar (5% hops).

Click to expand...

How did you arrive at your suggested dilutions?

Why use acetic acid when you can use citric acid? Cheap as dirt, less need be used and it has no smell.

GLS said:

Why use acetic acid when you can use citric acid? Cheap as dirt, less need be used and it has no smell.

Click to expand...

Because it has better keeping properties. The smell isn't objectionable for everyone. When dilute, it doesn't smell that much. When used for film in a tank, the smell isn't an issue. Quite frankly, there are things I've used that smell far worse. 25% ammonia is one of them.

Anon Ymous said:

Because it has better keeping properties

Click to expand...

True, but you can make up the citric acid solution fresh as a one-shot each time. It takes less than 30 seconds.

Anyway, to each their own.

faberryman said:

How did you arrive at your suggested dilutions?

Click to expand...

Well, I experimented heavily with both film and prints and this was the highest dilution that I could be comfortable with. At my dilution, there is NO QUESTION about an immediate, complete stop to all development. When I used the same solution for a second print it also stopped development immediately (was not slippery on the immersed hand). But by the third try, it was 'so so'. Thus, conservatively, I adopted these dilutions as perfect for the one-shot situation. Maybe you don't wish to change solutions after each print or so, but with film, it is the perfect 'solution' to adopt.

By the way, (and I have said this before) I have adopted a 'one tray' schedule for all my printing needs. I use small quantities of solution and empty the tray after each chemical time is up. This is best to do with only small prints (up to 5 x 7 or maybe up to 80 x 10). I have a 'dump' bucket ready and easy to reach in the dark (I never have used a safelight in over 50 years in the darkroom). I have measured quantities (according to tray size) of stop and fix ready to pour in the dark. I know that all of this sounds strange, but I would not go back to the three tray system for anything. This is actually easier and I have the decided advantage that each and every print attempt uses completely fresh solutions. My small quantities of solution are adequate, as I rock the tray for the duration of development and keep the print face down. I waste nothing and use no more chemicals than others do. After fix, I pour two changes of water: this prepares the tray to start with the next development and partially removes the hypo from the paper. The prints are washed, together, when I have finished.

I do a lot of things that are truly strange. For example, if I had all of Trump's money, I still would not use a washing machine, ever. I have not used one for at least three decades. Each night I wash clothes (or sheets or jackets) in a bucket filled with warm water, Dawn dish liquid, and a little bleach. This way, in 15 minutes I have washed, thoroughly rinsed, and wrung out to hang up to dry. I have NO accumulated dirty clothes and the cleanliness is, I feel, even better than with a washing machine. Better system for me, but, it sounds terrible to those who think they know better.

I have never tried citric acid for a stop bath. Honestly, why should I? Acetic acid is great, easily attainable, and one can even use household vinegar. I try not to look for trouble in life, but if someone utterly convinced me that citric acid had more advantages, I might try it. But, I am happy the way acetic acid works is and there is virtually no smell at my dilution. What most of you fail to understand about photo chemistry is that it is formulated to make up for the sloppiness that so many have. My developers, stop baths, and fixers are ALL highly diluted. For example, my fixer is used at one half paper strength for paper and at paper strength for films. My normal temp is 80F (my ambient) and I have NO problems with diluting in this way. Why work according to the 'sloppiness' that is factored into these formulas? I work intelligently, and I work without trying to get more out of my formulas. They work beautifully. For most film development I use the cheapest formula that can be considered, and it works beautifully: DEKTOL 1 + 24. That works well for Pan F+. For something like TMY 400 try 1 + 14. Times are within a good range: about 5 minutes for the Pan F and about 8 minutes for the TMY (at that 1 + 14 dilution). Sometimes the standardized literature does not remove the sloppiness factor (like ASA took forever to recognize that films are faster than the old speeds used to state). Remove the 'sloppiness' factor from your work. - David Lyga

GLS said:

True, but you can make up the citric acid solution fresh as a one-shot each time. It takes less than 30 seconds.

Anyway, to each their own.

Click to expand...

"Anyway, to each his/her own." Singular subject needs singular possessive pronoun. I know that GLS did not 'need' that correction (even though he needed it in order to be correct), but I detest this 'collective new grammar' that is rammed down our throats just because it is now deemed to be 'misogynist' to continue the masculine default that has guided the English language since the time of Shakespeare. (Moderators, forgive this necessary deviation.) - David Lyga

Sirius Glass said:

What a complete waste of chemicals. I am glad that you are no may accountant nor finance advisor.

Click to expand...

better than the archiver of lost negatives

psvensson said:

How do you agitate? Do you agitate the stop bath?

Click to expand...

same agitation for dev, stop and fix. consistency is key.

I haven't used a stop bath for film for 20 years, with no perceivable degradation of the negative. However I wash thoroughly between development and fix, about 2 minutes with multiple changes of water and constant agitation. The fixative shows no sign of contamination. I have an unopened bottle of ten year old Ilford Stop in the chemical cupboard, I'll use it when I next print for old time sake.

Stop Bath - How Important? I'd say very important to the contributors since the thread has now run for nearly 14 years
It may be less important to the OP or we have covered all the bases and he knows all there is to know since he was last seen about 2 years ago

pentaxuser

pentaxuser said:

we have covered all the bases

Click to expand...

and some of the acids too

As looooong as we are on the topic of stop baths (humor intended), the Film Developer Cookbook (Anchell and Troop, 1998) on page 103 recommends a running water stop bath. They list several disadvantages of using acid stop baths, most related to the effect of acid stop baths on the quality and integrity of the film emulsion. They also state that for several years (relative to the 1998 publication date of the book) Ilford has recommended a running water stop bath for film development.

Anchell and Troop do note that the nominal development time should be shortened slightly to account for the fact that a water stop bath allows development to continue slightly longer. In the Darkroom Cookbook (3rd edition, 2008, p. 104) Steve Anchell suggests that this would typically add about 15 seconds, but also if one is working up a development time using their own testing then that extra time will automatically be factored into the process as a result of the testing.

Personally, I don't see any advantage to using an acid stop bath. Even the argument that an acid stop bath is important if the film development time is short falls flat. The argument there is that small errors in the development time favor the use of an acid stop bath. However, if you do a careful error analysis you should conclude that the difference in negligible.

Let me work through a little math here. Case #1, assume a nominal development time of 2 minutes 45 seconds and assume an acid stop bath is used. Using an acid stop bath the effective development time will typically add about 15 seconds (Anchell, p. 104), for an effective development time of 3 minutes. Now assume that the person in the lab makes an error of 10 seconds in the nominal development time. That means that the effective development time could be anywhere between 170 and 190 seconds (180 +/- 10 seconds), or a +/- 5.6% error band in effective development time.

Case #2, assume a nominal development time of 2 minutes 30 seconds and assume a water stop bath is used. Using a water stop bath will add about 30 seconds to the nominal development time for an effective development time of 3 minutes. Now assume the lab makes an error of 10 seconds in the nominal development time. That means that the effective development time could be anywhere between 170 and 190 seconds, for a +/- 5.6% error band in effective development time. This is exactly the same error band in either case, so the argument that an acid stop bath is important if film development time is short does not make sense to me.

I am writing in the context of film development here. Print development might require a slightly different analysis, though I don't see why it would.

Alan, if I understand you correctly, using a stop bath adds 15 seconds (according to Anchell) but in actuality it adds zero if you consider transfer times being the same in water and acid stops. And, including transfer (or dump) times is correct. So this part of your argument goes out.

Also, you must consider the effect of size on uniformity wrt stop or water. Uniformity on one sheet or from process to process may vary.

And, how about the effect of pH 9 tap water vs pH 5 tap water?

PE

Looking at the example I just posted using slightly different parameters, suppose the variability is equivalent to 5% of the nominal processing time (i.e. 5% of 2 minutes 45 seconds vs. 5% of 2 minutes 30 seconds) but also suppose that the variability does not effect the development occurring the time in the stop bath. 5% of 2 minutes 45 seconds is equivalent to 8.5 seconds of development, whereas 5% of 2 minutes 30 seconds is 7.5 seconds. This is only a difference of 1 second effective development time, an utterly negligible difference.

Now, suppose that there is no variability during the nominal processing time, but during the stop bath there is an equivalent of 10% variability in the extra development time. 10% of 15 seconds is 1.5 seconds. 10% of 30 seconds is 3 seconds, for a difference of only 1.5 seconds of equivalent development time. Again, this is an utterly negligible difference.

Use stop bath or don't use stop bath. Your choice. I don't understand why this generates so much discussion.

I always use it...either just vinegar or citric acid.

faberryman said:

Use stop bath or don't use stop bath. Your choice. I don't understand why this generates so much discussion.

Click to expand...

Its not a choice its a mandate. In order to do proper Darkroom work you need to do what's necessary. I find it necessary to use water

Use what works - until it doesn't. Then use what is right.

There you go.

PE

Photo Engineer said:

Alan, if I understand you correctly, using a stop bath adds 15 seconds (according to Anchell) but in actuality it adds zero if you consider transfer times being the same in water and acid stops. And, including transfer (or dump) times is correct. So this part of your argument goes out.

Also, you must consider the effect of size on uniformity wrt stop or water. Uniformity on one sheet or from process to process may vary.

And, how about the effect of pH 9 tap water vs pH 5 tap water?

PE

Click to expand...

Maybe I was unclear in what I understand Anchell to have said. He did not advocate using an acid stop bath for only 15 seconds, but rather that film continues to develop for about 15 seconds when placed in an acid stop bath (depending somewhat on the pH of the acid solution). This is not to say that development continues at the full rate for 15 seconds and then stops abruptly at the end of 15 seconds. That would not be physically realistic. More likely it is a tapering off process that could be characterized by a time constant of about 15 seconds. This would be governed mainly by two processes, one of them (likely the slower process) would be diffusion of developer out of the emulsion. The other (likely much faster) would be the diffusion of hydrogen ions into the emulsion. Actually, it's not quite that simple either. Because of the constraint of charge balance, which is a rather strong constraint, hydrogen ions can't diffuse into the emulsion with dragging along the counter ion (e.g. acetate ion) at a concentration to maintain almost perfect local charge balance, but now we are getting a little too deep into the woods.

The situation with a pure water stop bath would differ in two main ways. First, the tapering off of the development process would be slower, with a characteristic time of more like 30 seconds according to Anchell. The first consequence is actually a result of the second consquence, which is that decreased development time would be dominated by diffusion of developer out of the emulsion, with diffusion of hydrogen ions into the emulsion being relatively less important, or not significant at all, depending on the pH of the water used for a stop bath. (There may be another effect to consider as well, which is the rate of diffusion of the developer's buffer out of the emulsion. That is an additional complication, but does not introduce any new principals into the analysis of the process.) For reference, the EPA recommends that suppliers of municipal drinking water keep the pH within the range of 6.5 to 8.5, so most tap waters are probably within this range. The actual pH value is not too important, as long as it is relatively stable from day to day, and assuming that one has developed the film processing parameters by testing. In any case, early in the process the acid/base balance within the emulsion is likely to be dominated by the residual buffer in the emulsion, along with the inherent buffering power of the gelatin itself. This will tend to partially dampen out any effect of the pH of the wash water.

Regarding evenness of exposure of the emulsion to stop bath (meaning exposing all of the surface of the film to the stop bath at the same time) that is obviously one condition for even development. However, it should affect an acid stop bath to the same extent as it affects a pure water stop bath. Some thought experiments should establish this on a theoretical basis, but for sake of brevity of an already-too-long post I won't attempt to present an analysis here.

Most of what I posted above is either theoretical or is based on information provided by others (mainly Anchell). The ultimate arbiter would be an experimental measurement, which I have not done. However (to break my comment about the post already being too long) a guy named Jay deFehr has done the experiments. I will quote what he reported in a post at another forum. I think he explains this more clearly than I can.

"Have you ever tried to measure the difference between using a stop bath and using plain water? I've tried, but could never measure a difference. Even if there was a measurable difference between using a stop bath and using plan water, it's irrelevant. What matters is consistency. Even if using a plain water rinse instead of an acid stop prolonged development by a few seconds, it would be the same few seconds for every roll, and have absolutely no effect on one's control of one's process. "

In another post in the same discussion thread Jay takes on another disputation which relates to the first. Here is what he said.

"I like to test these kinds of assumptions and urban myths, or used to like to. I formulated a developer that developed most films to normal contrast in about 45-60 seconds to test the claim that developing times under five minutes are too short for even development. I have to say, I knew going in this claim is false, because of rapid film processors used in the motion picture industry, but I wanted to show it was also false for home darkroom equipment and techniques. At the same time, I tested the claims about stop bath vs water rinse. These tests were done with as much precision as I could muster in my home darkroom. I used a sensitometer to make the exposures, processed in an automated film processor, and read the resulting step wedges with a densitometer. Even under these extreme conditions, the difference between using an acid stop and plain water was trivial. "

I am aware of Jay's work. I also posted above about stopping rate and diffusion. I'll extend that here.

We at EK coated a layer of indicator dye, then coated a thick pad of gelatin above that. We used that as a dye source in a cuvette in a spectrometer. Dumping in acid stop vs water showed that the neutralization of the indicator was instantaneous vs water. This was a pH 7 indicator. More sophisticated tests showed that that tiny hydrogen atom diffused almost infinitely fast vs all of the other ions present. In fact, IIRC, we never were able to get a figure on the actual rate of the H+ ion but could measure OH- which is not big at all. The HQ and other organics were lumbering beasts by comparison though.

The dye changed color quickly and uniformly over the sheets tested with acid, but changed in areas with the plain water.

BTW, this was done with and without agitation, but for the sake of the experiment, I don't believe that the agitation was very good - IMHO, at least as far as my memory serves.

In any event, this is one reason why Kodak recommended using a stop as per my earlier post.

PE

I can share that for many a moon I used an acid stop bath for sheet films and got pinholes in some but not all of the negatives. I highly recommend not using a stop bath for film as it has never happened since I just use plain water now.
that's about 5,000 negatives later!!