Stop Bath.. How important?

[RalphLambrecht]

Stop Bath
Once the desired degree of development has been
reached, the process must be stopped quickly to avoid
overdevelopment. This can be achieved through a
simple water rinse, but an acid stop bath is more
effective in neutralizing the alkaline activators and
stopping development almost instantaneously.
A dilute solution of acetic or citric acid makes
for a powerful stop bath. However, with developers
containing sodium carbonate, the acid concentration
must be kept sufficiently low to avoid the formation of
carbon-dioxide gas bubbles in the emulsion, because
this may lead to ‘pinholes’ in the emulsion.
in short, after conducting a proper film test, an acid stop bath is an efective way of using the test data and stopping development when we need to. thi avoids after developmentand confusing resultswith overdeveloped highlightsand unrealistic speed points. the question is not why/ it is why not?pinholes and air bubbles as a reaction with sodiun carbonate can also be avoided by using a half-strength stop bath for films.

 

[RalphLambrecht]

The manufacturers know best

Ian

as in the malboro commercial

 

[tim k]

I use acetic stop bath, because every roll of film or sheet of paper that is not stopped as such, a baby dolphin will die and I just can't stomach the thought of all those dolphins....

OMG.!! I did not know that. I wonder what citric acid could save....

 

[Photo Engineer]

With nothing between developer and fixer, it means that you are carrying a lot of crap into that fixer. It means that the fixer exhausts faster, and the chance of retained chemistry goes up!

As format size goes up, then a stop becomes more critical for uniformity. You must stop development quickly or you will get some sort of blemish on the final image. This is particularly important with LF and ULF films and very big enlargements.

PE

 

[George Collier]

PE - also true with Alkaline fixers, such as TF-4 and TF-5?

 

[Photo Engineer]

George, TF-5 is mildly acidic.

That said, YES I use a stop bath. After all, with TF4 there is no stopping action to speak of.

However, a rinse after the stop is useful with TF4 or TF5 to extend the life of the fix.

If you use only a water rinse, with no stop, you should use running water and not just a still water rinse. And, a rinse still can allow defects due to continued development.

PE

 

[Bill Burk]

There are long threads on the benefits..

Yay mods merged thread...

 

[RalphLambrecht]

OMG.!! I did not know that. I wonder what citric acid could save....

and save them from suffering a cold too

 

[eclarke]

The Haist book says that acid stop bath is important to condition the film gelatin for acceptance of fixer..

 

[Photo Engineer]

Grant does not say that a stop conditions the gelatin. What he does say is that a stop is important for uniformity and for maintenance of fixer activity and he does say that it is better than nothing at all and better than just a rinse.

He has nearly a chapter on this and it is permanently marked in one of my copies of Haist. Now, taken out of context and paraphrased, one might write that the gelatin is conditioned, but this word covers such broad territory, it could lead to another "myth" about analog photography!

PE

 

[Ian Grant]

Kodak state that a stop bath or water rinse is fine for films and we shouldn't forget that, it's fine in practice.

Kodak also use no sto bath or water rinse in some maxchine processors for film and that should lay a few myths to rest, but a water rinse or staop bath is far better practice.

Ian

 

[Steve Smith]

If the fix is not going to be re-used, is there any reason (real, not mythology) why a film can't go straight from developer to fix?


Steve.

 

[doughowk]

Several years ago a commercial lab improperly processed some film for me - pinholes that were likely due to too acidic a stop bath. For film I would think too drastic of ph changes could cause problems. If both developers and fixers are alkaline, a water rinse or even an alkaline stop (sodium metasulfite?) would be safer.
Looked up in Anchell & Troop and suggested alkaline formulae appears to include sodium metaborate and sodium bisulfite. But can't find an exact formulae.

 

[Steve Smith]

Another question: As we have both alkaline and acid fixers, is it possible to have a neutral fixer?


Steve.

 

[Ian Grant]

Most alkaline fixers are closer to neutral and even fixers like Hypam & Ilford rapid fixer are only slightly acidic at pH 5.4. Black coffee is more acidic

Ian

 

[Steve Smith]

Then why the fuss about fixers bleaching images? The users of staining developers are particularly fussy about this!


Steve.

 

[removed account4]

Most alkaline fixers are closer to neutral and even fixers like Hypam & Ilford rapid fixer are only slightly acidic at pH 5.4. Black coffee is more acidic

Ian

dang!
now i think i am going to start using "coffeeshop", black coffee stopbath together with sumatranol and seawater fixer i am
all set for the next mayan apocalypse !

thanks for the 411! ian

drinking his arabica
john

 

[Photo Engineer]

TF-5 is nearly neutral. In fact, it is the most nearly neutral of all B&W fixers.

Going directly into the fix though carries developer into the fix which is not good, throw away or not! You have to remove as much of this junk as possible before you go into the fix so that the fixing action takes place in the absence of HQ, Phenidone, Metol and whatever else could be in there.

The changes in pH have been there for ages. Early processes used a stop and had no real problems. Going from developer to acid stop to alkaline fixer certainly changes swell, but I have tested it and it works even with TF-4. And, no matter what you do, you will have changes in swell due to the ionic strength of the solution (or just water) and pH changes. After all, a ph 10 developer followed by a pH 6 city water rinse followed by a pH 8 TF-4 or a pH 4.5 Acid Fix certainly does not hurt anything.

PE

 

[Steve Smith]

The only staining developer I have used it Prescysol. It is advised to use an alkaline fix with this but I have seen no difference in my own negative with acid or alkaline.

I'm sure if there was a reduction of stain with an acid fix, it would be dependent upon the time spent in the fix.


Steve.

 

[Photo Engineer]

Any staining that takes place in film or paper may take years and years to show up. I have generally seen that bad stains take as little as 5 years to show up, and moderate stains take 15 - 20 years or more. So, don't talk about seeing no stains until you have looked at your prints in 20 years.

PE

 

[Ian Grant]

The only staining developer I have used it Prescysol. It is advised to use an alkaline fix with this but I have seen no difference in my own negative with acid or alkaline.

I'm sure if there was a reduction of stain with an acid fix, it would be dependent upon the time spent in the fix.


Steve.

That's the experience of many others, the stain isn't affected by the use of normal fixers ith pH's in the region of 5.2/5.4. Prescsol is a clone of Pyrocat HD so behave the same way.

I've run tests with prints processed in a Pyro developer and the stain is very stable and unaffected by fixer.

Just to quash another myth -stains from using Pyro developoers don't suddenly appear after a number of years. Stains particularly with FB prints do show up after time and that might be years from inadequate fixing/washing but that can happen with any developer.

Ian

 

[alanrockwood]

I have only read a few pages of this thread, but with regard to using water as a stop bath (or wash if one prefers to call it that), water is the standard stop bath used in phototherm processors.

With regard to a degree of continued development when using water vs. acidic stop bath, the only reason this could be bad is if the continuation of development is both pronounced and uneven. Assuming the continuation of development is uniform it is not a problem, and if one is worried about the extra development using a water stop bath, then just cut the main development time by a small fraction of the total.

 

[Photo Engineer]

Alan, for the sake of uniformity, the need for a stop goes up with size and is more important with paper than film due to shorter development times.

A running water rinse is better than a static rinse in order to reduce carrryover into the fix. This becomes critical with higher pH fixers.

PE

 

[nolanr66]

I developed a roll of Tri-x 35mm today and decided to see how it went without a stop bath. Instead I put in 300ml of Brita filtered water and swished it around with the twister stick for 5 seconds. Then went on to the fix and what I found was the exposure was excellent and the other thing I discovered was the negatives were very clean afterwards. I guess my stop bath was to old and dirty. Anyway I am going to skip the stop bath portion for developing the film. I do not believe it is of any usefulness at least for a home processor like myself.

 

[MattKing]

I developed a roll of Tri-x 35mm today and decided to see how it went without a stop bath. Instead I put in 300ml of Brita filtered water and swished it around with the twister stick for 5 seconds. Then went on to the fix and what I found was the exposure was excellent and the other thing I discovered was the negatives were very clean afterwards. I guess my stop bath was to old and dirty. Anyway I am going to skip the stop bath portion for developing the film. I do not believe it is of any usefulness at least for a home processor like myself.

If you insist on using a water rinse, it needs to be in continuously chanving water, and for much longer than 5 seconds.
Do you re-use your stop bath? I don't, unless I have more film to develop that day.
Do you re-use your fixer? I do, and the use of stop bath helps extend life of the fixer. In addition to making my development more consistent.
If your fixer is either alkaline or has a neutral ph, it is particularly important to either use a stop bath or to thoroughly rinse the film in continuously changing water.