A blended ferrocyanide print process

Raghu Kuvempunagar said:

Sounds great! Let us know how it goes with the students.

What inkjet paper have you been using?

The stain issue is generally due to the buffer in the paper which needs to be neutralised before coating. Impure Copper Sulphate and high humidity could also be other causes as noted by Andrew.

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I will probably be a few more weeks before I get the students involved, so I still have some time to get my own process worked out a little better. So far as I know, there are no buffers in the inkjet paper. I have a huge supply of cheap watercolor papers, and I know that they are buffered. I soaked some tonight in citric acid and the bubbled, so they probably have a pretty high alkaline load. I tried this paper last week and the emulsion had turned blue even before exposure; I'll see if the acidification helps. As for inkjet paper, I've used three. First, Kodak Professional glossy. I bought a ton of it because I had a profile for my printer. That printer died, Kodak stopped supporting the paper, and I'm too lazy to create my own profiles, so I've been using it for cyanotypes. Second, some Red River Metallic gloss. It's not great for every subject, but some landscapes look fantastic on this paper. Finally, there are a lot of half-printed photos at the lab in school, and I take those failed photos and cut off the unused paper. That stuff is Arista Pearl.

jmoche said:

I have a huge supply of cheap watercolor papers, and I know that they are buffered. I soaked some tonight in citric acid and the bubbled, so they probably have a pretty high alkaline load. I tried this paper last week and the emulsion had turned blue even before exposure; I'll see if the acidification helps.

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It should, even for the Cyanotype process.

jmoche said:

I certainly understand the idea behind your "stick to one paper" suggestion. I'm still in the process of finding which paper I prefer. I have not tried ammonium chloride precoating. Can you point me to an explanation of the process? Thanks!

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based on what Raghu said, and being easily to me to use Fabriano Bristol I picked that paper. I precoat it with a 1% solution of ammonium chloride. I noticed that I double precoat it I get deeper blacks. the precoating allows you to get clean white but for the deep black is vital to tone the processed print with the ammonia-copper-sulphide toner. to make it you need to add ammonia on a copper sulphide solution until it change it's colour to a vibrant deep blue. you will notice when it's done. you don't need to be precise with it's concentration, the only thing that change by changing it it's how long it will tone. just add some copper and than ammonia by drop.

let me know how it goes!