What is happening here? Van Dyke Brown variant?

I was playing around with cuprotype/cyanotype/vdb chemicals, and did a funky mix.

10g water, 4g ferric ammonium citrate, 1g citric acid, 0.4g thio, and 5g 5% silver nitrate solution.

The printed out image pre-washing is nearly invisible. But then I did a coat with a 10% copper II sulfate solution (just brushed on), and got a deep rich brown. What is the source of the brown? I would have assumed the thio would have reacted with the silver nitrate in solution, and wasn't really expecting to get an image.

Dry print:




Still wet, with longer exposure time and a very high-contrast image of my own (not a photo, a drawing):

@fgorga may have some ideas on this.
Welcome to Photrio!

Yeah, I too would have thought adding AgNO3 to thiosulfate should have produced brown precipitates - does it not do that or does the solution stay clear?

Also, does the image form immediately as you brush CuSO4 or after you put it in water?

:Niranjan.

nmp said:

Yeah, I too would have thought adding AgNO3 to thiosulfate should have produced brown precipitates - does it not do that or does the solution stay clear?

Also, does the image form immediately as you brush CuSO4 or after you put it in water?

:Niranjan.

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It seems to when I coat the page (darker than a van dyke), but much of it washes off.

The very slight image that appears after exposure might be the FAC? It's a very faint yellow, invisible in low light.

The image forms immediately upon brushing on the copper sulfate. There also appears a very dark (almost black) liquid that washes off when I put it in water.

kaelynlayne said:

It seems to when I coat the page (darker than a van dyke), but much of it washes off.

The very slight image that appears after exposure might be the FAC? It's a very faint yellow, invisible in low light.

The image forms immediately upon brushing on the copper sulfate. There also appears a very dark (almost black) liquid that washes off when I put it in water.

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What if you not brush CuSO4 and just wash it Or brush plain water?

:Niranjan.

nmp said:

What if you not brush CuSO4 and just wash it Or brush plain water?

:Niranjan.

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No image forms at all, the page is the color of the highlights.

If you have ferricyanide, try toning with it. If it changes tone, we would know it is a copper image and not silver.

:Niranjan.

nmp said:

If you have ferricyanide, try toning with it. If it changes tone, we would know it is a copper image and not silver.

:Niranjan.

Click to expand...

I didn't forget about this! I fell down the rabbit hole and did a bunch of tests, will post another update later today with more images.

Applying potassium ferricyanide turned the whole page pink, with a very faint brown image still visible (no variation in the pink hue, just flatly pink, all discernable parts of the image were still brown). Sometimes I mess up the cuprotype and the highlights stay this shade of pink (I'm assuming when I don't adequately wash out the copper, but unsure), but the shadows are always still a darker red hue. So I don't think it's purely copper forming the image?

Interestingly, applying a 10% copper sulfate solution to a normal rinsed but untoned and unfixed VDB also formed a light pink image with discernable bleaching--highlights remained white, shadows were pink, will post photos later.

I very much like the grey-brown hue that coating a VDB+thio in copper sulfate produces (especially with longer exposure time), but the first couple of prints I do tend to bleach out. Then the brush and solution get contaminated with something from the VDB+thio (something in the highlights or shadows?) and it all works perfectly.

Variations to test today:
- FAC alone, expose, coat in copper sulfate post-exposure, see what happens?
- try 1% copper sulfate instead of 10%. 5% doesn't display any discernable difference in effect.
- I'm wondering if I could add anything to the copper sulfate to consistently get it to develop the VDB+thio properly, if brush contamination has this effect? I tried thio alone and it didn't make any real difference. If it's something in the highlights, I could try something like silver nitrate + thio in case it's a silver thiosulfate complex?

Any other things I should try?

Example of bleaching, which lessens as the brush becomes contaminated:


Original (underexposed, with some bleaching):


After applying potassium ferricyanide:

Oh, and coating the VDB+thio in copper sulfate post-exposure produces a sulphurous smell. Maybe a useful clue?

nmp said:

If you have ferricyanide, try toning with it. If it changes tone, we would know it is a copper image and not silver.

:Niranjan.

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I'm still not sure how I managed to get a brown image initially (maybe improperly mixed citric acid? I'm not the most careful), but I can consistently get a very pretty silver image by washing in 3% copper sulfate.

The pink staining was because the sensitized sheet wasn't totally dry prior to exposing. I'm also impatient. The silver image is probably actually silver, it bleaches with potassium ferricyanide. I'm assuming it's a double displacement, and the copper precipitates silver out of the thio-silver complex. Basically a salt print, but cheaper than toning a cuprotype in silver nitrate.

kaelynlayne said:

cheaper than toning a cuprotype in silver nitrate.

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This is interesting as I had done some experiments some tme ago in silver nitrate toning of Copper Thiocyanate prints (Jim Patterson's Cuprotype process) and I had mixed experience. I got nice reddish pink toned prints in some cases and significant smudging in some other cases.

Do you have examples of your silver nitrate toned cuprotype prints? Are these hypo-cuprotype prints? I'm curious to know what colour tone they produced when toned in silver nitrate.

Raghu Kuvempunagar said:

This is interesting as I had done some experiments some tme ago in silver nitrate toning of Copper Thiocyanate prints (Jim Patterson's Cuprotype process) and I had mixed experience. I got nice reddish pink toned prints in some cases and significant smudging in some other cases.

Do you have examples of your silver nitrate toned cuprotype prints? Are these hypo-cuprotype prints? I'm curious to know what colour tone they produced when toned in silver nitrate.

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I never did (I couldn't justify making up a bath that would likely get wasted, very pricey), but @Bronson Dugnutt did here: https://www.photrio.com/forum/threads/a-new-cuprotype.193432/page-5#post-2762354

I get the same tones using this formula (10g water, 4g ferric ammonium citrate, 1g citric acid, 0.4g thio, and 5g 5% silver nitrate solution; post exposure bath in 3% copper ii sulfate) that he did with a silver-toned cuprotype, without having to develop back.

The copper bath I use here is pretty finicky, it took me a while to figure out what exactly was happening. Too dilute (around 1-2% or less) and it washes away; too concentrated (above 10%), and the image bleaches. Brushing on the developer doesn't work, unfortunately—too much smudging/bleaching—but my next step is to remove the citric acid in the sensitizer and see if this speeds up development time, maybe making brushing less impractical. I feel like I could get greater dmax if it "worked" faster, right now the reaction seems to take a second or so to really "set."

kaelynlayne said:

I never did (I couldn't justify making up a bath that would likely get wasted, very pricey), but @Bronson Dugnutt did here: https://www.photrio.com/forum/threads/a-new-cuprotype.193432/page-5#post-2762354

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Thanks for the link. @Bronson Dugnutt's results look very different from mine, mostly because I toned Copper Thiocyanate print (Jim Patterson's process) and here it is Copper Thiosulphate/Ferricyanide print that's being toned/developed.

I needed very little Silver Nitrate solution for toning as I used a cotton ball to coat. Toning in a tray full of Silver Nitrate solution would be obiously expensive.

I should give it a try again and hopefully get smudge free prints.

Raghu Kuvempunagar said:

Thanks for the link. @Bronson Dugnutt's results look very different from mine, mostly because I toned Copper Thiocyanate print (Jim Patterson's process) and here it is Copper Thiosulphate/Ferricyanide print that's being toned/developed.

I needed very little Silver Nitrate solution for toning as I used a cotton ball to coat. Toning in a tray full of Silver Nitrate solution would be obiously expensive.

I should give it a try again and hopefully get smudge free prints.

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Eliminating citric acid definitely reduces the amount of smudging. I believe citric acid slows down the reaction, and the faster the reaction the less smudging (but could be totally off-base!). In the attached image, I was able to brush on 10% copper sulfate with no issue. I think the paper has to be a tiny bit grippy (I get smudges still with watercolor paper, running a few more tests today to confirm), but maybe try eliminating or reducing the citric acid in Jim Patterson's process?

kaelynlayne said:

the attached image,

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That looks great!

Jim's Cuprotype process works fine. It's in the silver nitrate toning that I faced the smudging problem. The toning process is described in a 19th century publication. No citric acid is involved in the toning process as far as I recall. I'll give it another try in the future, but as Niranjan said elsewhere, it's a rather long path to silver print.

Raghu Kuvempunagar said:

it's a rather long path to silver print.

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Personally I like this process better than a straight salt print, but only because I don't like having to soak pages in salt. I do a lot of my work out of a hotel room while traveling, and I don't like carrying around trays and solution bottles in addition to my suitcase full of chemicals