Okay, how does alkaline stop bath actually work?

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Interestingly, Agfa-Gavert B&W reversal process doesn't use an acid stop bath and instead uses a wash. The first developer is surely highly energetic and alkaline and the wash step is like a two bath development. I wonder why uneven development wasn't a concern in this process.
 

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Although not illustrated it does say the negatives are rinsed after development.

It's also worth noting that pre-WWII fixers were much simpler and sold as raw chemicals, so the 1940 Kodak Ltd Professional Catalogue lists Hyypo (Sodium Thiosulphate) and Potassium Metabisulphite.

The history of Stop Baths and Fixers appears to be over-looked :D

Ian
 

miha

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Although not illustrated it does say the negatives are rinsed after development.

It's also worth noting that pre-WWII fixers were much simpler and sold as raw chemicals, so the 1940 Kodak Ltd Professional Catalogue lists Hyypo (Sodium Thiosulphate) and Potassium Metabisulphite.

The history of Stop Baths and Fixers appears to be over-looked :D

Ian

It's a fascinating topic; before the photo forums, I was only aware of the liquid fixers (FF-2 from Fotokemika), now I'm all too confused with two bath/double strength/sodium/1-minute/alkaline and what not fixing technique, and now alkaline stop baths...😲
 

MattKing

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I'm thinking that that Ilford chart doesn't show an acid stop because all the vinegar in England was needed for the chips. :whistling:
 

Ian Grant

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I'm thinking that that Ilford chart doesn't show an acid stop because all the vinegar in England was needed for the chips. :whistling:

And the pickled eggs sold in all our Pubs :D Chicken Tikka Masala from Indian takeaways is now more popular than fish and chips.

It's a fascinating topic; before the photo forums, I was only aware of the liquid fixers (FF-2 from Fotokemika), now I'm all too confused with two bath/double strength/sodium/1-minute/alkaline and what not fixing technique, and now alkaline stop baths...😲

There's a history of stop baths, which includes the use of very dilute Hydrochoric or even Sulphuric acids, Potassium Metabisulphite solution, for tropical worked acidified Potassium Alum tanning solutions, Chrome Alum Stop Hardener which was the best hardening stop bath - I used it with EFKE Kb14 in the early 1970s until finding adding a few drops of Formaldehyde to the developer was a better option.

Ian
 

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I think maybe one of Haist's concerns about uneven continuation of development with a water bath instead of stop is unevenness in the time it would take the water to mix into the emulsion to dilute the developer, not just the pour-in time, but this is a total guess. (For dilution you need some large number, say 10-20 units of water to contact each unit of developer, but for altering the pH you only need of order 1 unit of stop to reach each unit of developer.)

My Kodak (USA) Reference Handbook from 1946 discusses acid stop baths with the conventional reasons for use, and also gives formulae for SB-1 through SB-5 - includes acetic acid, chrome alum, and hardening stop baths. It has formulae for developers and fixers, but also an extensive list of which chemicals are sold in premade packets or containers, so that was already common practice in the US in 1946.

I learned to use acid stop bath when learning in the 1980s from Kodak manuals, books, and older relatives. I don't think I ever heard that there were pitched battles over stop bath until the internet.
 

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I don't think I ever heard that there were pitched battles over stop bath until the internet.

That may be because in truth the pitched battles may be caused by the entrenched position taken on the subject by a few rather than a true "fight to the death" for the real and only truth 🙂

pentaxuser
 

albada

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That may be because in truth the pitched battles may be caused by the entrenched position taken on the subject by a few rather than a true "fight to the death" for the real and only truth 🙂

pentaxuser

One can fight for the truth or his belief; the two are often not the same.
But this thread in Photrio shows another reason to fight -- for the fun of it.
 

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Fun thread! I thought Stop Bath only worked because it was an ACID and developers were BASIC. I guess I was basically wrong!
 

Ian Grant

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I think maybe one of Haist's concerns about uneven continuation of development with a water bath instead of stop is unevenness in the time it would take the water to mix into the emulsion to dilute the developer, not just the pour-in time, but this is a total guess. (For dilution you need some large number, say 10-20 units of water to contact each unit of developer, but for altering the pH you only need of order 1 unit of stop to reach each unit of developer.)

My Kodak (USA) Reference Handbook from 1946 discusses acid stop baths with the conventional reasons for use, and also gives formulae for SB-1 through SB-5 - includes acetic acid, chrome alum, and hardening stop baths. It has formulae for developers and fixers, but also an extensive list of which chemicals are sold in premade packets or containers, so that was already common practice in the US in 1946.

I learned to use acid stop bath when learning in the 1980s from Kodak manuals, books, and older relatives. I don't think I ever heard that there were pitched battles over stop bath until the internet.

The wartime Kodak Research Laboratories Formulary W.1 1944 seems to be the first publication of Kodak Formulae, of course individaul formulae had been published from Eastman Kodak's early days. It does include stop baths and calls them Acid Rinse, under the heading Rinse and Hardening Baths. Army and particulary RAF units were mixing some of their chemistry from raw chemicals, the BJP Almanacs of the time show formulae devised in the field by RAF officers.

Hans Windisch's book on modern ways of working "Die Neu Foto Schule" German, The New Photo School" English published in 1938 makes no mention of stop baths. It seems that stopbaths come into more common use during WWII, this is also a point where there were significant improvements in emulsions, Ilord FP3 and HP3 were introduced around 1941.

I have a set of those Eastman Kodak Reference Handbooks, in their original boxes, there were 4. Kodak Professional Handbook, Kodak Reference Handbook 1, Kodak Reference Handbook 2, Kodak Color Handbook. Seems that there were also UK versions as I have a Kodak Ltd, Harrow, Kodak Chemicals and Formulae section in a searate Kodak Refernce Handbook 2.

Ian
 

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Oddly the "Kodak Reference Handbook 1", 1946, states for most films "rinse thoroughly in water", then fix, others it adds "or Kodak Stop Bath SB-3 (during hot weather), SB-3 is a Potassiun Chrome alum hardener. Kodak are recommending a stop bath with papers at this point but not for films, except the strong hardening bath in hot weather.

Part of the reason for the use of a stop bath with paper is the far greater carry over of developer alkali into the fixer if a water rinse is used, because at that time all papers were fibre based, a water rinse is sufficient with film.

Ian
 
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