Ansco 130 with potassium carbonate???

[Steve Goldstein]

The formula for Edwal 120 in The Darkroom Cookbook 4ed suggests substituting Sodium carbonate for Potassium carbonate for a less warm tone.

Has anyone ever tried Ansco 130 with the opposite substitution, i.e. Potassium carbonate instead of Sodium carbonate? It’s easy enough to figure out the weight of K2CO3 needed to get the same concentration of carbonate ion.

 

[koraks]

I do wonder what the rationale and validity is of the potassium vs. sodium exchange. I wouldn't expect much (any) difference.

 

[john_s]

Two possible rationales: one is that it's said that potassium salts give warmer results in paper developers, and the other is that they are more soluble which could be an advantage if you're making up a more concentrated stock (which might keep better and will take up less space).

I use potassium carbonate to make up triple strength ID-78, to make storage easier and possibly to prolong storage. Does it make any difference to the warmth? Not that I can tell, with Ilford WT FB paper.

 

[koraks]

one is that it's said that potassium salts give warmer results in paper developers, and the other is that they are more soluble which could be an advantage if you're making up a more concentrated stock (which might keep better and will take up less space).

Thanks, but: #2 I know and often use, similar to your ID78 example. #1 I can deduce from the OP, but it's what makes me wonder why and if this is the case. Like you, the difference never struck me. Admittedly, I haven't tested for it specifically, hence the question.

 

[john_s]

Although it would be interesting, one way or the other, I don't feel inclined to mix up two batches, one of each, to test the difference. Using only a Nova vertical slot processor in my tiny darkroom would make it even more arduous. There would still be quite a lot of sodium in it from the sulphite, and I don't think that potassium sulphite is easy to source here. If it were, an all-potassium version would be more interesting.

 

[TomR55]

Years ago, I mixed Ansco 130 with either potassium or sodium carbonate to obtain slightly cooler or warmer tones, respectively. I would also use 1% benzotrizole solution to slightly modify tones.

IIRC some papers responded with some subtle shifts, others did not--for example, Kodak Elite (long gone), responded to such modifications but others less so. I understand that Foma, Ilford and other manufacturers are providing similar papers ... so it might be a worthwhile endeavor.

 

[relistan]

Two possible rationales: one is that it's said that potassium salts give warmer results in paper developers

Very interesting. I had not read that before, thanks.