Stop bath strong enough for Amidol

Jarin Blaschke · Nov 22, 2017

Hi:

My usual stop bath for film and prints is 15g of citric acid in a liter of water. I don't have any acetic acid around, and would prefer to keep it that way. I've been printing with amidol and chloride paper this year and I wonder if I need to strengthen it, given how powerful amidol is - the developer itself has 3g of citric acid in it already. The short developing times with chloride (I use 60-90 sec) probably require a total halt of development for accuracy and consistency. I've seen no apparent issues yet with my 15g, but I've only been "proofing" and not really fine printing with matching prints.

Any strong opinions on the matter?

Jarin

Andrew O'Neill · Nov 22, 2017

I prefer citric acid stop baths. I only ever used 3 or 4 teaspoons in a litre of water, even for Amidol developed paper. If it's working, just stick with it.

Peter Schrager · Nov 22, 2017

I use 28% glacial for prints...try it and see

Gerald C Koch · Nov 22, 2017

Peter Schrager said:
I use 28% glacial for prints...try it and see

Its either 28% or glacial (98%) but it cannot be both.

Photo Engineer · Nov 22, 2017

Remember that Amidol develops in acidic solution, so a stop is not guaranteed to stop unless the developer is diluted enough and acidified well.

PE

Craig · Nov 22, 2017

If Amidol develops in acid shouldn't the stop be a base?

Photo Engineer · Nov 22, 2017

No, because Amidol develops in Alkali as well.

PE

Alan9940 · Nov 22, 2017

I use 100ml of 28% acetic acid to 2L water for Amidol developed prints and I've never noticed any issues with this combo.

Jarin Blaschke · Nov 23, 2017

Photo Engineer said:
Remember that Amidol develops in acidic solution, so a stop is not guaranteed to stop unless the developer is diluted enough and acidified well.

PE

The developer I'm using is this:

Water: 1L
Sodium Sulfite: 30g
Citric Acid: 3g
Amidol: 10g
1% Benzotriazole: 40ml

Today, the stop I used is this:

Water: 1L
Citric Acid: 20g

With what I'm using, do you think I'm achieving a full stop?

Jarin

dE fENDER · Nov 23, 2017

Jarin Blaschke said:
With what I'm using, do you think I'm achieving a full stop?

Jarin

Amidol begins to develop at pH 4, so check the ph of your stop.

Photo Engineer · Nov 23, 2017

There are ways to check out continued development, but the above post pretty much says it all.

PE

mshchem · Nov 23, 2017

When in doubt use pH

Jarin Blaschke · Nov 24, 2017

dE fENDER said:
Amidol begins to develop at pH 4, so check the ph of your stop.

Thanks - looks like I need to get a ph meter! Do we have consensus that I just need ph below 4?

Photo Engineer · Nov 24, 2017

I vote YES!

Gerald C Koch · Nov 27, 2017

Jarin Blaschke said:
The developer I'm using is this:

Water: 1L
Sodium Sulfite: 30g
Citric Acid: 3g
Amidol: 10g
1% Benzotriazole: 40ml

Today, the stop I used is this:

Water: 1L
Citric Acid: 20g

With what I'm using, do you think I'm achieving a full stop?

Jarin

Citric or lactic acid is sometimes ADDED to Amidol developers to increase the tray life of the developer. It's addition is otherwise not necessary. Usually the acid is not even listed as part of the formula leaving it up to the user to add it if needed.

juan · Nov 28, 2017

Look at Michael A. Smith’s website. Unfortunately this iPad will not allow me to type in the url. It’s Michael and Paula .com all run together. Michael has used amidol and citric acid stops for decades.

Stop bath strong enough for Amidol

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