Copper Toning Cyanotypes

[IconicTyphoon]

I'm still working my way through RK's blended FC developer thread, https://www.photrio.com/forum/threa...nide-print-process.212808/page-8#post-2903570 , but I'd like to share the results of my dabbing.

I extrapolated from a patent mentioned in Ware's Cyanomicon. Here's the developer formula I came up with:
12.5g cuso4
0.5g na2co3
500ml household clear ammonia
500ml h20

These are the test strips I made with classic cyanotype. They were dry and had been made in the usual manner, before dipping in the developer. It's a nice black.

Here's what I think is happening: the alkali is splitting the prussian blue into iron(iii)hydroxide and free ferrocyanide. Copper(ii) reacts with the iron(iii)hydroxide to yield copper(ii)hydroxide which decomposes to copper(ii)oxide and water. Copper(ii)ferrocyanide is also formed.

When I soaked a test print in a diluted developer, I ended up with a ghost cuprotype on the back.

 

[Andrew O'Neill]

EEEEK! More stuff I have to try! Thanks for sharing!

 

[Andrew O'Neill]

So... you soaked a dried Cyanotype in your copper/carbonate/ammonia developer?

 

[koraks]

Welcome aboard @IconicTyphoon !
That toning method seems to work very nicely. Coincidentally I had been doing something similar when I was combining cyanotypes with Van Dyke a few weeks ago. I just used some plain copper sulfate solution; I must try adding some carbonate and ammonia as well to render it more effective.

 

[bernard_L]

@IconicTyphoon : Congratulations for this very interesting result. How would you compare the end result with toning in tannic acid?

I feel slightly frustrated seeing small tearouts. Could you please post examples of complete images, both before (plain cyanotype) and after toning.
Also curious as to what heuristics guided you to this formulation. And why the two alkalies? The two cations have different solubility properties with iron/copper?

 

[nmp]

Doesn't CuSO4 form Cu(OH)2 or CuCO3 precipitates instantly when you mix it with ammonia and/or Na2CO3? I would have expected so.

:Niranjan.

 

[Raghu Kuvempunagar]

Doesn't CuSO4 form Cu(OH)2 or CuCO3 precipitates instantly when you mix it with ammonia and/or Na2CO3? I would have expected so.

:Niranjan.

When Sodium Carbonate is added, a precipitate does form. But it goes into solution as Ammonia is added producing a deep greenish-blue solution. Actually, this is a fairly well-known copper toner, when combined with Ferricyanide, for silver gelatin prints. I've used it previously in my FerroBlend process but it produces too much stain and hence didn't pursue it further. Here, OP has used to tone normally developed Cyanotype, and the image forming pigment in this case is mostly Copper Hydroxide or Copper Oxide. I think a final toning in a Sulphide or Seleno-Sulphide toner will give a more brown coloured print.

The ammonical copper toner is discussed here:
https://woelen.homescience.net/science/photo/toners/ferrocyanide.html

 

[nmp]

When Sodium Carbonate is added, a precipitate does form. But it goes into solution as Ammonia is added producing a deep greenish-blue solution. Actually, this is a fairly well-known copper toner, when combined with Ferricyanide, for silver gelatin prints. I've used it previously in my FerroBlend process but it produces too much stain and hence didn't pursue it further. Here, OP has used to tone normally developed Cyanotype, and the image forming pigment in this case is mostly Copper Hydroxide or Copper Oxide. I think a final toning in a Sulphide or Seleno-Sulphide toner will give a more brown coloured print.

The ammonical copper toner is discussed here:
https://woelen.homescience.net/science/photo/toners/ferrocyanide.html

Thanks Raghu. Makes sense. I was not aware of this phenomenon. Learned something new.

:Niranjan.