Acidic stop with PyroCAT-HD

[swmcl]

Hi,

I have read that Sandy King recommends a 1/4 to 1/2 strength acid stop bath after developing with PyroCAT-HD.

I want to know which acidic chemicals can be used for the purpose without compromising the staining effect given by the developer.

There are a great number of citric acid based stops available but I believe citric acid reduces or removes the stain.

Thanks for your help as always,

Steve.

[Sanjay Sen]

He does? I wasn't aware of that. The article (http://unblinkingeye.com/Articles/Pyrocat/pyrocat.html) I always refer to when I use Pyrocat-HD says to use a plain water stop bath.

[swmcl]

Please refer to this article on Unblinking Eye.

See step 3 under 'General Development Procedures'

http://unblinkingeye.com/Articles/PCat/PCat2/pcat2.html

Rgds,

Steve

[swmcl]

I should have mentioned that the reason I'm trying to get a final answer on the subject is because acetic acid is hard to acquire - especially the glacial variety.

B&H - and others I'm sure - only sell it over the counter. It is attracting a hazmat fee too.

Alternatives are needed for me.

I'm at the other end of the world where just about everything is mail order only.

Steve

[phil sweeney]

http://www.largeformatphotography.info/forum/showthread.php?t=58802&page=3

[swmcl]

Thanks Phil,

In that thread I see Andrew ONeill uses a citric stop bath (top of page 2). I assume it is a reduced dilution.

There is no specific mention of stain or tanning reduction.

1 level tablespoon is 15g citric acid powder. When mixed with 1 litre of water this is the normal strength working solution as I understand it.

My chem days are long gone. I assume I should mix say 3-5g per litre for a suitable working solution. This would be up to a 1/3rd strength solution (?)

Using this for a minute or two after developing my film and before fixing seems to be a general practice.

I was hoping someone would have tried different acidic stops and dilutions to know which ones were OK and at what strength.

Thanks again,

[Bjorn Nilsson]

I should have mentioned that the reason I'm trying to get a final answer on the subject is because acetic acid is hard to acquire - especially the glacial variety.

B&H - and others I'm sure - only sell it over the counter. It is attracting a hazmat fee too.

Alternatives are needed for me.

I'm at the other end of the world where just about everything is mail order only.

Steve

You can use normal household white vinegar, which is acetic acid in a diluted form. Check the label for the contents. In Sweden it's usually 28% strong, while glacial is closer to 100%. Just see to that you get "white vinegar" and not "white wine vinegar" which is more suited for your salad. :)

About the OP, I usually do a good flush with two quick changes of water, which I try to time at about 30 seconds each. I havn't compared using a weak (1/2 to 1/4 strength stop bath) to water only, but the reason I use the stop bath at all is to conserve the fixer. I'm quite sure that the water flush is sufficient to stop the developing action.

//Björn

[Brian Stein]

I use a water stop. IIRC this will not stop developing action, but dilutes down the dev to preserve fixer action. If you are normally swift of hand this does not seem to be an issue. Given there are quite a few folks around doing this I wouldn't sweat too hard.

I had read the unblinkingeye recipe, but had completely forgotten the dilute acid bit, and focussed just on the "....If the stop bath is too strong it will reduce image stain..." bit, hence my choice of the water stop.

As the principal action of the stop bath is to change pH and render dev inactive I doubt the acid matters tooooo much so citric should work. Scandinavian vinegar is obviously much stronger than Aus, the local vinegars Ive seen top out at about 10-12%.

[Bjorn Nilsson]

Oh yeah, sorry. The swedish "ättika" usually comes in two different strenghts, with and without the "syra" (acid) suffix. Without the suffix it's somewhat like 10-12% and with the suffix (indicating stronger stuff) it's 28%.

//Björn

[Jim Ewins]

If the image isn't over exposed, the developer has mostly finished at least so that a water stop is effective. Using PMK pyro an alkaline fixer like TF-4 is recommended.

[D. Bryant]

You can use normal household white vinegar, which is acetic acid in a diluted form. Check the label for the contents. In Sweden it's usually 28% strong, while glacial is closer to 100%. Just see to that you get "white vinegar" and not "white wine vinegar" which is more suited for your salad. :)

About the OP, I usually do a good flush with two quick changes of water, which I try to time at about 30 seconds each. I havn't compared using a weak (1/2 to 1/4 strength stop bath) to water only, but the reason I use the stop bath at all is to conserve the fixer. I'm quite sure that the water flush is sufficient to stop the developing action.

//Björn

White vinegar is usually more expensive than acetic acid.

[Andrew O'Neill]

I use 5% vinegar because it's readily available and dilute it down to about 1%. I also use citric acid. One table spoon in a litre of water does me. I've never seen a reduction in stain with citric acid.