Curious for an answer: stop bath in the RA4 process

David Lyga · Mar 15, 2019

I am curious to know WHY the pH has to be a bit higher for RA4 printing than for B&W. This is all I have read, in that the 'same' stop can be used for either but with pH being a bit higher for the RA4. Sodium sulfite is usually added to the RA4 stop, I believe because it scavenges the developer and, thus, helps prevent staining with blix. I have always used the SAME (VERY dilute) stop formula for both B&W and color (2.5 glacial acetic acid per liter, one shot), but, I do make certain to wash the color neg for at least a minute or two because I use potassium ferricyanide with fixer for my blix, and that combination hates even a vestige of developer in its midst (staining). - David Lyga

trendland · Mar 15, 2019

David Lyga said:
I am curious to know WHY the pH has to be a bit higher for RA4 printing than for B&W. This is all I have read, in that the 'same' stop can be used for either but with pH being a bit higher for the RA4. Sodium sulfite is usually added to the RA4 stop, I believe because it scavenges the developer and, thus, helps prevent staining with blix. I have always used the SAME (VERY dilute) stop formula for both B&W and color (2.5 glacial acetic acid per liter, one shot), but, I do make certain to wash the color neg for at least a minute or two because I use potassium ferricyanide with fixer for my blix, and that combination hates even a vestige of developer in its midst (staining). - David Lyga

I am not sure if I have just bad remind at this moment?
But is it not in oposite direction? Bw fix should not be used for c41 because it is too strong (from ph)! But c41 fix can be used for bw fix??? Hmm is it not the same with stop bath to RA4?
The oposite? Have to look first to my notes! Obviously I mixed it - like so often!

with greetings David

PS : If your workflow over all the years you've used stop bath to boths was quite OK - the difference
from ph should be just smal! Otherwise you should have noticed it meanwhile.

trendland · Mar 15, 2019

OK here I am back - well if you use a stop bath for RA4 you are RIGHT if you have eine with a 2% solution of acid!
If you would decide between 1,25%/1,75%/2,25% up to 3% is it in you!
I would imagine you decide in lowest concentrated stop bath to save acid solution David (just a smal joke - never mind)
The function of stop bath has not the mich impact to following baths as many others would excpect! The live of folowing baths are more in concern of using seperate baths or Blix!
So your Ra4 stop bath has more the function to STOP (as the name indecates) the RA4 development!
Perhaps (I can imagine) this is also done with normal water (via delution of remaining developer concentration) if .....well if there not is the issue from developer bath coming from decontamination
into following baths!

Well and if I don't have forgotten an other important issue - your workflow would be most precise
if you use a stop bath from concentration of you personal reference (between around 1,5% - 3%)
and following water bath (to give the remaining developer the absolute rest)!
But from logical concern (regarding ph of the stop bath) there should be no further need for water bath! (but it would not be wrong.....)

Of course the same concentration is fine to stop bw paper development!

with regards

PS : I never used stop bath with bw papers! Therefore I remember quite well the cheapness of bw
fixer in the good old days! After weeks I had to change the fixing bath!

May be that my water stop worked quite sufficiant all the time! !
(lousy workflow I know.....)

David Lyga · Mar 15, 2019

Yes, I feel that the extremely dilute stop bath both saves money (least important) and also is sufficient if you use one shot processes, as I do. I have always used B&W fixer after the stop bath for both C41 negs and RA4 paper with no problems, as long as there is a wash after the fix. My process is: dev, stop, fix, wash, blix. I get great results. But I wanted to know WHY the literature says to make the stop for color more alkaline. I understand the sulfite part (although I don't use it). - David Lyga

trendland · Mar 15, 2019

OK now I first unterstand your question right! You use Blix AND you prefer additional WASH step atfter stop - right! OK - so the "recomandation" of higher ph to RA4 stop bath should have to do with different ph of normal RA4 developer in comparison of ph of normal bw developer!
So the different value of RA4 ph has the function of "COMPENSATION" - that should be right from theory but in practice it is also done from the time you hold your papers into RA4 stop bath!
It may be an issue to the livetime of your RA4 stop (but who cares about livetime of stop bath..)
Specialy if you use a further wash after stop!
I gues it goes more about quality and precision of your RA4 print development AND livetime of your Blix!

with regards

trendland · Mar 15, 2019

different value of "RA4 stop bath ph" sorry

with regards

David Lyga · Mar 15, 2019

So the points you bring up are largely moot, trendland, thus really unimportant. I use 'one-shot' for everything, so I don't care about lifetime past the actual, specific process. I don't seem to need a specific pH to 'acclimate' the fix or blix: everything works out well. But I was curious to ask this question because it is 'required' over and over in the literature. (Focal Encylopedia of Photography). - David Lyga

trendland · Mar 15, 2019

Oh oh oh......I have the idea now that some experts came on the plan and will
"tore up previously made statements"

I will state in advance : " There are allways many ways to guide to Rome"

with regards

PS : you use "bleach" at final step David because "blix" is the modern way (fix and bleach i one bath)

trendland · Mar 15, 2019

Aha David - well if you delute everything as "one shot" sorry perhaps I missunderstood something again yes David -then it is realy from no interest for "livetime" of bath!

Coming to litherature : of course there are recomandations not the same to each personal workflow!
But this is (so is it to me) caused from recomandation of each manufacturer concerning the specific
soupe (regarding Kodak for example) and in this point. wie are common again (I shurely agree with you) manufacturers ALLWAYS recommand to use more of their stuft (from concentration of from less time in use) because of what?????

Some say :to be in the safe side (if you look at the specifics - you are sometimes "on the extreme safe side". so of course : THEY SOMETIMES WANT TO SELL MOST VALUES OF THEIR STUFF!

That is clear

with regards

PS : Litherature is in concern of different " manufacturers ways" but acid is acid (no impact who manufactures it!)

koraks · Mar 15, 2019

David Lyga said:
I am curious to know WHY the pH has to be a bit higher for RA4 printing than for B&W.

I'm not sure if this is necessarily the case. I use the same stop bath for both B&W and RA4, with no problems. Some caveats:
1. At low pH, some dyes remain in their leuco/white state. However, subsequent baths of higher pH should resolve this. Perhaps if the pH is too low at some point, certain dyes may be locked in their leuco state, but I really don't know. I never noted anything along those lines with RA4, and ECN-2 (different animal, I know) uses a sulfuric acid stop bath of decidedly low pH (around 2, but a bit lower seems to work too with no apparent problems).
2. It has been said by some that citric acid, which is often used as odorless stop bath, should not be used in color processes. I once queried PhotoEngineer on this and he remembered it too, but didn't exactly know why. I see no difference between an acetic acid stop bath and citric acid stop bath in RA4 processing, but I never use citric acid for film processing.

BTW, I never use sulfite in color stop baths.

David Lyga said:
I do make certain to wash the color neg for at least a minute or two because I use potassium ferricyanide with fixer for my blix, and that combination hates even a vestige of developer in its midst (staining)

Yes, ferricyanide does appear to give humongous fog on film when developer is carried over into it. For ECN-2, I use a ferricyanide bleach as per Kodak specifications. I make sure to wash thoroughly between stop and bleach for that reason. Too low pH combined with a ferricyanide bleach may result in formation of prussian blue, which is another thing to keep an eye out for.

David Lyga · Mar 15, 2019

koraks said:
I'm not sure if this is necessarily the case. I use the same stop bath for both B&W and RA4, with no problems. Some caveats:
1. At low pH, some dyes remain in their leuco/white state. However, subsequent baths of higher pH should resolve this. Perhaps if the pH is too low at some point, certain dyes may be locked in their leuco state, but I really don't know. I never noted anything along those lines with RA4, and ECN-2 (different animal, I know) uses a sulfuric acid stop bath of decidedly low pH (around 2, but a bit lower seems to work too with no apparent problems).
2. It has been said by some that citric acid, which is often used as odorless stop bath, should not be used in color processes. I once queried PhotoEngineer on this and he remembered it too, but didn't exactly know why. I see no difference between an acetic acid stop bath and citric acid stop bath in RA4 processing, but I never use citric acid for film processing.

BTW, I never use sulfite in color stop baths.

Yes, ferricyanide does appear to give humongous fog on film when developer is carried over into it. For ECN-2, I use a ferricyanide bleach as per Kodak specifications. I make sure to wash thoroughly between stop and bleach for that reason. Too low pH combined with a ferricyanide bleach may result in formation of prussian blue, which is another thing to keep an eye out for.

Thank yoy so much for the information, koraks. This is a topic that is, unfortunately, too often not discussed. There are many problems that are ascribed to other causes because 'stop bath' is considered so trivial, That is, apparently, not the case. - David Lyga.

trendland · Mar 15, 2019

koraks said:
I'm not sure if this is necessarily the case. I use the same stop bath for both B&W and RA4, with no problems. Some caveats:
I see no difference between an acetic acid stop bath and citric acid stop bath in RA4 processing.

I guess there IS no difference. To come to the right ph is the task! Wich sort of acid the job is done from isn't the issue! Beside this two options I should add - because other chemical acids may cause
problems to films and to health.........

with regards

David Lyga · Mar 15, 2019

trendland said:
PS : you use "bleach" at final step David because "blix" is the modern way (fix and bleach i one bath)

NO, I use blix after the fix. Why? Because I reverse the process. If I used bleach, THEN fix, there would be no problem. But when you first use fix, the exposed silver is still present as a component of the image (in addition to the dye). A subsequent bleach would not remove it completely. The blix, however, does remove ALL silver to leave only a dye image.

That does bring up an interesting situation, whereby if you fixed the negative ONLY after development, you would obtain an image that would be a bit more contrasty, because that image would comprise both dye and exposed silver. I think that some Hollywood movies were done that way in order to provide a different perspective. Other than that, I cannot say more, other than say that fixing ONLY does no long term harm to the image, it just makes it, and the base as well, darker. But all that can be 'printed through'. and you could obtain a highly satisfactory print - David Lyga

koraks · Mar 15, 2019

trendland said:
I guess there IS no difference. To come to the right ph is the task! Wich sort of acid the job is done from isn't the issue!

Citric acid is a chelating agent, whereas acetic acid isn't. That's at least one difference between them that may be relevant.

David Lyga said:
That does bring up an interesting situation, whereby if you fixed the negative ONLY after development, you would obtain an image that would be a bit more contrasty, because that image would comprise both dye and exposed silver.

It's usually called 'bleach bypass' and it is indeed sometimes used in the movie industry, but it works on your own still materials as well. With film, you'll note increased grain, increased contrast and reduced saturation. With paper, the grain still isn't visible and otherwise it's analogous to film.

trendland · Mar 15, 2019

koraks said:
Citric acid is a chelating agent, whereas acetic acid isn't. That's at least one difference between them that may be relevant.

It's usually called 'bleach bypass' and it is indeed sometimes used in the movie industry, but it works on your own still materials as well. With film, you'll note increased grain, increased contrast and reduced saturation. With paper, the grain still isn't visible and otherwise it's analogous to film.

Hmm - therefore acetic asid (glacial) might be recomanded for e6 processing stop bath?
Can't remember wich I used? In the past I used acetic asid but at last I just prefered citic asid because it is such easy to buy (and cheapeest)

with regards

trendland · Mar 15, 2019

David Lyga said:
NO, I use blix after the fix. Why? Because I reverse the process. If I used bleach, THEN fix, there would be no problem. But when you first use fix, the exposed silver is still present as a component of the image (in addition to the dye). A subsequent bleach would not remove it completely. The blix, however, does remove ALL silver to leave only a dye image.

That does bring up an interesting situation, whereby if you fixed the negative ONLY after development, you would obtain an image that would be a bit more contrasty, because that image would comprise both dye and exposed silver. I think that some Hollywood movies were done that way in order to provide a different perspective. Other than that, I cannot say more, other than say that fixing ONLY does no long term harm to the image, it just makes it, and the base as well, darker. But all that can be 'printed through'. and you could obtain a highly satisfactory print - David Lyga

Understand David - well my RA4 workflow is since a couple of years under "construction" because
I missed my superior darkroom! The new one is much smaller so I used it most for film processing
AND bw printing! So it is hart to remind on RA4 - from the good old days...

with regards

BMbikerider · Mar 15, 2019

Me thinks you have a solution that needs a problem!

I don't think I will be far off the mark when I say I probably have been doing C41 and RA4 processing for more years than most on this forum. I have never ever had a problem with using a normal indicator stop bath at a standard dilution when using either process. (I always use an acetic acid type) For every litre of stop bath I use in the process for 10 films and for every litre of bleach/fix (for film). I replenish with 10cc of either per film. (24 or 36 exp - you cannot over replenish). In theory it should last forever with the replenishment but after 10 film I change for new.

Likewise for RA4, the stop bath is standard dilution (used in a NOVA 12x16 processor) and like the developer and blix for every 10 sheets of 8x10 paper I replenish with 100cc of individual working solution chemical per slot.

Yes I have had failures - not many, but these can all be attributed to problems other than chemical. - Usually temperature/time and sometimes exposure .

RPC · Mar 15, 2019

PE has said a 1-2% solution of acetic acid is suitable for both color and b&w printing. I don't recall him saying sulfite is necessary nor have I ever heard that for RA-4.

The color stop pH can be higher than b&w, but doesn't have to be. Bleach-fix pH is low enough to itself to have an effect on stopping development. I develop RA-4 in trays and use no stop bath although I would recommend it for drums to avoid streaking.

Photo Engineer · Mar 15, 2019

The stop for B&W and RA4 can be the same as long as the blix pH is 5.5 - 6.7 and the wash is sufficient to remove all chemistry. This is for proper dye hue and stability.

PE

DREW WILEY · Mar 17, 2019

I use acetic acid for both, but well below 2%. It doesn't take much. But I do RA4 one-shot chem in drums. A replenished roller transport processor system might need 2% for a margin of safety.

mshchem · Mar 17, 2019

I have been given enough Kodak Indicator Stop Bath to last 3 lifetimes. I use it for RA4 and b&w film. Stinks too much for open trays, I use the Ilfostop (citric acid), I've been given for b&w paper.

Photo Engineer · Mar 17, 2019

I have been told never to use a citric acid stop for color. I have forgotten the reasons.

PE

Raghu Kuvempunagar · Mar 18, 2019

Photo Engineer said:
I have been told never to use a citric acid stop for color. I have forgotten the reasons.

PE

It's probably something citric acid does to the dyes. When I used citric acid stop bath with Ilford XP2 Super, I got a base colour which was a lot more darker than normal.

BMbikerider · Mar 18, 2019

I tried Citric Acid based stop bath once a good few years ago for printing using a NOVA deep-tank. Then I was away for 2 weeks and when I returned there was a healthy growth of hairy fungus growing on the top of the stop bath channel. I have never used it again for film or printing, either B&W or Colour I know I am not alone in having had this problem

Photo Engineer · Mar 18, 2019

Add 1 g/l of Benzoic Acid to your Citric Acid stop to prevent this growth. It might help.

PE

Curious for an answer: stop bath in the RA4 process

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