Cupric sulphate - mixing copper toner

LarsAC · Aug 18, 2017

Hi (Ex-)APUGers,

I'd like to mix some copper toner and found two forms of cupric (copper) sulphate: CuSO4 "pure" (anhydrous?) and the pentahydrate form.

Which form is usually referred to in common recipes for toners? I know, I can easily convert amounts between the two forms using their molar weights, but need to know which one is the reference point in e.g. a Dassonville T-5 toner recipe.

Any ideas / experiences ?

Thanks,
Lars

Gerald C Koch · Aug 18, 2017

Usually when the hydrate is not specified it is the one most stable at normal room temperature and humidity. This would be the perta hydrate. Just a word of caution, you may not be satisfied with the results. These old toner formulae were intended for older papers which contained various heavy metals such as lead and cadmium. When the EPA forced these papers off the market the newer papers in general responded more weakly to toning. So you may not be able to reproduce the red color that this toner was said to produce.

LarsAC · Aug 18, 2017

Thanks for clarification, Gerald.

I'll give it a try, I am curious and also have some Portriga and original MCC if I don't like the results on modern papers. Anyway, I'm not after real red, rather some different type of brown compared to thiourea or sulfide.

Lars

nmp · Aug 18, 2017

LarsAC said:
Hi (Ex-)APUGers,

I'd like to mix some copper toner and found two forms of cupric (copper) sulphate: CuSO4 "pure" (anhydrous?) and the pentahydrate form.

Which form is usually referred to in common recipes for toners? I know, I can easily convert amounts between the two forms using their molar weights, but need to know which one is the reference point in e.g. a Dassonville T-5 toner recipe.

Any ideas / experiences ?

Thanks,
Lars

You would be better off buying the pentahydrate anyway - it's much cheaper even after considering the molar mass differences, more easily available and it is not hygroscopic like the anhydrous version - easier to handle and store. Most likely the formula would have called for the hydrated version. Don't you hate when you read the formula published without regards to the different forms of the chemical that might be available.

LarsAC · Aug 18, 2017

Sorry, did not mention explicitly, but exactly for the reasons you describe, I would have bought the pentahydrate form anyway. The question was more, if a conversion of the amount specified in a recipe is indeed needed or not. For sure, the usual sources could be more accurate on this.

Lars

nmp · Aug 18, 2017

LarsAC said:
Sorry, did not mention explicitly, but exactly for the reasons you describe, I would have bought the pentahydrate form anyway. The question was more, if a conversion of the amount specified in a recipe is indeed needed or not. For sure, the usual sources could be more accurate on this.

Lars

So I checked my copy of The Chemistry of Photography (1940). The formula only lists "copper sulfate." But then I looked at the back of the book where all of the chemicals are described. The description for the Copper sulfate is CuSO4 + 5H2O.

The formula for Copper Toner is:

A:
Copper Sulf 60 grains
Pot Citrate 240 grains
Water to make 20 ozs

B:
Pot Ferri 50 grains
Pot Citrate 240 grains
Water to make 20 ozs

Not sure how this compares to the T-5.

Hope this helps....

LarsAC · Aug 19, 2017

Not sure about grains and oz, but the relation of the chemicals is virtually the same. Looks like it is the right approach to use the pentahydrate.

Thanks for looking up another resource!

Lars

Cupric sulphate - mixing copper toner

LarsAC

Gerald C Koch

LarsAC

nmp

LarsAC

nmp

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