Will Sodium Carbonate(washing soda) work as hypo clearning agent?

[baachitraka]

I use simple Sodium Sulphite solution as hypo clearning agent for prints and wonder whether Sodium Carbonate will do the same job?

 

[Ian Grant]

Yes, it was recommended by Agfa (as Michael says). Like Sodium Sulphite Sodium Carbonate also works partly by Ion exchange it's less efficient though.

Ian

 

[baachitraka]

Right now I mix 10g/l of sodium sulphite to make HCA and leave the prints in the tray for 10-15mins. Will 20g/l of sodium carbonate have any effect on efficiency or any effect at all?

How to determine the quantity to mix, whether it is Sodium Sulfite or Sodium Carbonate(if works)?

My major is not chemistry and I understand they are different salts and their interaction with thiosulfates and silver thiosulfate complexes can be different.

 

[Ian Grant]

Michael, it's certainly not ancient history it's still the recommended method for some papers, in their "current" datasheets, 3 minutes in a 1% bath of Sodium Carbonate (anhydrous) so 2% for Crystalline (washing soda).

Ian

 

[Gerald C Koch]

Agfa recommended using sodium carbonate 1% solution as a washing aid. However both it and sodium sulfite are cheap. Why use something that is not as effective. If you have reasonably hard water both chemicals will cause precipitation and the solution will quickly turn cloudy. This can leave a sediment on prints. That is why HCA contains a calcium sequestering agent and is buffered to be slightly acid. I posted an HCA substitute formula on APUG search the archives.

 

[RauschenOderKorn]

I would assume that the effect you get is different:

The Sodium carbonate will neutralize the acidity from the stop bath and fixer which might have soaked into the fiber base and damage the print during a long period of storage.
The Sodium sulfite helps to remove thiosulfate from the print which might have an adversary effect for storage or toning.

In any case, always washing your prints thoroughly is the most important factor, any "washing aid" is always only an "aid".

 

[Ian Grant]

I would assume that the effect you get is different:

The Sodium carbonate will neutralize the acidity from the stop bath and fixer which might have soaked into the fiber base and damage the print during a long period of storage.
The Sodium sulfite helps to remove thiosulfate from the print which might have an adversary effect for storage or toning.

In any case, always washing your prints thoroughly is the most important factor, any "washing aid" is always only an "aid".

It's not just about Carbonate neutralising, you have to realise that as well as Sodium Sulphite other Sodium salts will work including Sodium Citrate, Sodium Phosphates, Sodium Chloride. Agfa claimed that as well as cutting washing times the Carbonate bath helps increase print durability.

Ian

 

[RauschenOderKorn]

... you have to realise that as well as Sodium Sulphite other Sodium salts will work including Sodium Citrate, Sodium Phosphates, Sodium Chloride. ...

Can you please elaborate on this? The sodium salts your a mentioning have all different effects and chemical properties, e.g. a solution of Sodium Sulphite is alcaline and prevents oxidation, a solution of NaCl is neutral and won´t have any effect on oxidation.

My understanding is the following: sodium sulphite is best suited as HCA as it is alcaline thus dehardening the Emulsion, neutralizing any acid residuals from the fixer and the Sulfite as a pre-product of the Thiosulfate will help to dissolve any byproducts from the fixing process.

 

[RauschenOderKorn]

A little note on the side:

Ralph

If you prefer a low pH level HCA try this

EDTA4Na 12g or DTPA pentasodium salt (solution) 25ml
Sodium sulfite 200g
Sodium bisulfite 6g
Sodium citrate 4g

to make 1000ml stock solution
dilute 1+9 for working solution

Wolfgang Moersch
www.moersch-photochemie.de

 

[Ian Grant]

Can you please elaborate on this? The sodium salts your a mentioning have all different effects and chemical properties, e.g. a solution of Sodium Sulphite is alcaline and prevents oxidation, a solution of NaCl is neutral and won´t have any effect on oxidation.

My understanding is the following: sodium sulphite is best suited as HCA as it is alcaline thus dehardening the Emulsion, neutralizing any acid residuals from the fixer and the Sulfite as a pre-product of the Thiosulfate will help to dissolve any byproducts from the fixing process.

G.I.P. Levenson of Kodak Research (Harrow, UK) did work in this field. There's two different things happening which is why Sulphite followed by Carbonate are more efficient than neutral or mildly acidic sodium salts. First it's the alkalinity and some of the semi-soluble intermediary Silver-Thiosulphate complexes being more soluble in an alkali solution and secondly the presence of Sodium ions tipping equilibrium balances again making semi-soluble complexes more soluble. About 40 years ago I drew up a schematic of all the equations and the intermediary complexes taking place during fixing (based on current theories of that time), it wasn't simple chemistry.

Ian

 

[baachitraka]

I can buy Sodium Carbonate as Domol waschsoda in Rossmann. Yeah, I can order Sodium Sulfite from Suvatlar but Rossmann is cheap if that works.

 

[mdarnton]

Sodium Sulfite is used in swimming pools, and I was able to order quite a large bag of it on Ebay for ridiculously cheap. I imagine you might find the same in Germany.

 

[Xmas]

Supposedly even sea water is effective.
The negatives from the austere WWII ASW corvettes with limited Drinking water tankage were as good or better than the negatives from larger vessels with desalinisation.
They only did a final in fresh water.
Even better availability today given the ice is melting.

 

[tezzasmall]

Supposedly even sea water is effective.
The negatives from the austere WWII ASW corvettes with limited Drinking water tankage were as good or better than the negatives from larger vessels with desalinisation.
They only did a final in fresh water.
Even better availability today given the ice is melting.

Resurrecting to ask, has anyone more recently than WW2, used sea water as an effective hypo clearing agent?

I ask as I live just a couple of miles from the sea, so I have a lot 'on tap', so to speak and anything that can help me cut down my usage of lovely fresh and clean tap water is a bonus.

Terry S

 

[Rudeofus]

Yes, AFAIK it is still effective, i.e. it gets thiosulfate out of photographic materials faster than tap water or distilled water. It is not as effective as Sodium Sulfite or Sodium Carbonate in water, but given your location, it appears to be a whole lot cheaper.

 

[Raghu Kuvempunagar]

Is Sodium Carbonate also effective when used as a substitute for Sodium Sulphite in clear bath after Ferricyanide/Dichromate/Permanganate/Copper Sulphite bleach?

 

[Rudeofus]

If you wash film after fixation, at first most of the Thiosulfate gets out through diffusion, after which washing slows down significantly, especially if an acidic hardening fixer was used. That remaining Thiosulfate holds on to the gelatin matrix, so regular diffusion principles do no longer apply. If Sodium Sulfite is then added to the wash water, there will be an ion exchange between thiosulfate and sulfite, and the remaining thiosulfate will leave the gelatin rather quickly. A similar, but somewhat slower ion exchange takes place between thiosulfate and carbonate or thiosulfate and chloride. This is the principle behind HCA. Hypo eliminator bathes would accomplish this goal by oxidizing the thiosulfate to sulfate, thereby turning it into a stable compound which will not damage image silver over time.

A similar process might also happen when you wash out bleaches, but the clearing bath used after bleaching also serves a second purpose: it has to deactivate the remaining bleach agents. Sulfite does this in its role as strong reducer, and carbonate won't fit this role. Therefore carbonate might somewhat speed up removal of bleaching agents, but it will not stop them out like sulfite does.

If you want to see it like this, the sulfite used in clearing bathes after bleaching acts as bleach eliminator bath rather than a bleach clearing agent.

 

[Raghu Kuvempunagar]

If you want to see it like this, the sulfite used in clearing bathes after bleaching acts as bleach eliminator bath rather than a bleach clearing agent.

This was very insightful! Thanks Rudy.

 

[tezzasmall]

This was very insightful! Thanks Rudy.

Indeed it was.

Terry S

 

[Ian Grant]

If you wash film after fixation, at first most of the Thiosulfate gets out through diffusion, after which washing slows down significantly, especially if an acidic hardening fixer was used. That remaining Thiosulfate holds on to the gelatin matrix, so regular diffusion principles do no longer apply. If Sodium Sulfite is then added to the wash water, there will be an ion exchange between thiosulfate and sulfite, and the remaining thiosulfate will leave the gelatin rather quickly. A similar, but somewhat slower ion exchange takes place between thiosulfate and carbonate or thiosulfate and chloride. This is the principle behind HCA. Hypo eliminator bathes would accomplish this goal by oxidizing the thiosulfate to sulfate, thereby turning it into a stable compound which will not damage image silver over time.

A similar process might also happen when you wash out bleaches, but the clearing bath used after bleaching also serves a second purpose: it has to deactivate the remaining bleach agents. Sulfite does this in its role as strong reducer, and carbonate won't fit this role. Therefore carbonate might somewhat speed up removal of bleaching agents, but it will not stop them out like sulfite does.

If you want to see it like this, the sulfite used in clearing bathes after bleaching acts as bleach eliminator bath rather than a bleach clearing agent.

Actually it's the bonding of intermediary complexes formed by the Silver and Thiosulphate that's the issue usually forming weak bonds with cellulose in Fibre based paper base. I do have the reactions listed somewhere it's something I looked at in the mid 1970's.

There's very little bonding between these complexes and the gelatin which is why there lille purpose using an HCA with fims and RC papers. The complexes become an issue in silver laden fixers where equilibrium reactions are retarded which is why two bath fixing is better for FB papers. Films and RC papers can tolerate much higher silver content in fixing baths.

Ian