HCA: Can I substitute Sodium Sulfite with Sodium Carbonate

My home made HCA contains just 20 gm of Sodium Sulfite in a liter of water, in which I soak prints for five minutes.

Mean-time I am reading caffenol blogs in which they use Sodium Carbonate and that made me wonder whether I can substitute Sodium Sulfite with Sodium Carbonate in my home made HCA.

I vaguely remember that Sodium Sulfite reacts with ammomium thiosulfate forms certain compounds that do not stain the prints, but I have no idea how Sodium Carbonate can play a role in removing fixing agents.

Agfa used to recommend Sodium Carbonate as a wash aid for their fibre based papers, you can use it.

Ian

Michael is right the carbonate causes the emulsion to swell aiding in the egress of thiosulfate ions. The mechanism appears to be that sulfite ions push the thiosulfate ions off of their sites in the emulsion allowing them to pass out of the emulsion faster. I believe that Adfa recommended a 1% solution of the anhydrous salt. You will need a calcium sequestering agent if you want to use tap water. Note that Agfa recommended its use for papers not film.

I intend to use only for Agfa MCC 110. Sodium Carbonate is available in drug store chain and they are very cheap.

May I ask, what results in yellow stain on the paper if not washed properly?

I have read it somewhere, it is thiosulfate breaks into simpler salts and on particular salt turn to yellow but I do not know the specific name of those salts.

I have always been very pleased with the results using Tetenal Lavaquick.

The data sheet says that the key chemical components are:

Tetrasodium ethylene diaminetetraacetate / EDTA- sodiumsalt | 10-25%

Potassium Carbonate | 5-10%

Ilford's Washaid has the following key chemical components:

SODIUM SULPHITE | 5 - 10%
EDTA | 1 - 5%
SODIUM ALKYL ETHOXY SULFATE | 0 - 1%
POLYMETHYLSILOXANE | 0 - 1%

The USA's favourite Perma Wash has the following key chemical components:

AMMONIUM SULFITE, MONOHYDRATE | Less than 20%
SODIUM 2-ETHYLHEXYL SULFATE ETHYLHEXYL SULFATE, SODIUM SALT | Less than 5%

So no Sodium Carbonate there in any of the leading brands.

It would appear only Agfa suggested using Sodium Carbonate.

Bests,

David.
www.dsallen.de

@Michael, may I ask you what causes the yellow stain on papers when not thoroughly washed.

baachitraka said:

My home made HCA contains just 20 gm of Sodium Sulfite in a liter of water, in which I soak prints for five minutes.

Mean-time I am reading caffenol blogs in which they use Sodium Carbonate and that made me wonder whether I can substitute Sodium Sulfite with Sodium Carbonate in my home made HCA.

I vaguely remember that Sodium Sulfite reacts with ammomium thiosulfate forms certain compounds that do not stain the prints, but I have no idea how Sodium Carbonate can play a role in removing fixing agents.

Click to expand...

2% sodium sulfite is the active ingredient in HCA but as Ian already said different companies recommended different ingredients for was aid and sodium carbonate was recommended by Agfa.I believe did research on sodium chloride but in the end sodium sulfite proved to be the most efficient, Still, you can use sodium carbonate and was Agfa style. Give it a try and report.