Formula for a quicker cuprotype (on par with cyanotype)

[kaelynlayne]

Adding a small amount of silver nitrate to the cuprotype solution significantly decreases exposure time.

Here's the formula I have used: 10mg water, 1mg ferric ammonium citrate, 0.4g sodium thiosulfate, 0.6g copper ii sulfate, 1.2g 5% silver nitrate solution

The end result looks identical to a cuprotype, but with much quicker exposure time.

 

[kaelynlayne]

I was intrigued by @Jan de Jong 's initial experiments with copper ii sulfate and wanted to see if silver nitrate played a role in his images—it definitely seems to!

I hope I managed to tag correctly, apologies if not
{Moderator note: no worries; fixed!}

 

[fgorga]

Adding a small amount of silver nitrate to the cuprotype solution significantly decreases exposure time.

Here's the formula I have used: 10mg water, 1mg ferric ammonium citrate, 0.4g sodium thiosulfate, 0.6g copper ii sulfate, 1.2g 5% silver nitrate solution

The end result looks identical to a cuprotype, but with much quicker exposure time.

Very interesting! This is a great improvement to the process. The slow exposure of cuprotype is, in my mind, its biggest flaw.

I assume that you mean 10 mL of water in your recipe not 10 mg. Is that correct? The same for the amount of silver nitrate solution... did you actually use 1.2 g or do you mean 1.2 mL?

Have you tried varying the silver content, especially trying smaller amounts? The chemist in me wonders if the silver could be acting as a catalyst. In which case small amounts could be just as effective.

My thought about mechanism goes like this... the ionic silver(I) would be reduced by the light to metallic silver(0) and is then re-oxidized back to silver(I) while reducing the copper(II) to copper(I). In other words the silver provides an alternate/additional path to copper(I). The rest of the chemistry of cuprotype would be unchanged.

Additionally, have you "stress tested' a print to see if there is residual silver in the print. I would do this by placing a fully processed and dried print in the bright sun for at least several hours. If the print darkens significantly, especially in the highlights, I would think that there is still unreacted silver present. If so, I would try fixing the cuprotype with sodium thiosulfate as one does for a salted paper print.

I have put trying this on my to do list.

 

[kaelynlayne]

I assume that you mean 10 mL of water in your recipe not 10 mg. Is that correct? The same for the amount of silver nitrate solution... did you actually use 1.2 g or do you mean 1.2 mL?

Have you tried varying the silver content, especially trying smaller amounts? The chemist in me wonders if the silver could be acting as a catalyst. In which case small amounts could be just as effective.

My thought about mechanism goes like this... the ionic silver(I) would be reduced by the light to metallic silver(0) and is then re-oxidized back to silver(I) while reducing the copper(II) to copper(I). In other words the silver provides an alternate/additional path to copper(I). The rest of the chemistry of cuprotype would be unchanged.

I measured everything out in g when I mixed everything together. So 10g water by weight (not mg, that was a typo), and 1.2g of 5% AgNO3 solution. I know it's not the most precise or exacting way of mixing chemicals, but I use alt techniques to essentially make prints of my own art. It ends up looking somewhat like a woodblock print. I can be a little freer with technique than the tonal scale of photographs demands.

I haven't looked into substantially smaller amounts, but definitely want to! I tried 1g initially, it worked just fine. I did 1.2g one time by mistake, thought the Dmax was *slightly* better (maybe) and just ran with it. But I'm very curious, and will write up the results the next time I fiddle with it.

I'll stick a print in the sun tomorrow and report back. I was getting 5 minute exposures the other day in bright sun, and probably could have done 30 seconds to a minute less.

 

[Raghu Kuvempunagar]

Interesting finding. Congratulations!

I have some questions and suggestions in this context:

What is the improvement in speed that you obtained?

Is it possible to eliminate Thiosulphate completely or reduce it to the minimum amount absolutely required to get further speedup? The printout might not be strong after exposure but development in ferricyanide could make it stronger.

Would this also speedup Jim Patterson's Cuprotype process?

If speed is the main concern you may want to try @Cor's adaptation of Copper Printing process. It is at least as simple as hypo-cuprotype but much faster.

 

[kaelynlayne]

Is it possible to eliminate Thiosulphate completely or reduce it to the minimum amount absolutely required to get further speedup? The printout might not be strong after exposure but development in ferricyanide could make it stronger.

I'm not sure! I assumed it was the silver-thiosulfate complex specifically that was speeding up the process, so didn't even bother to try reducing or eliminating the thiosulfate. Copper sulfate does cause silver to precipitate out in solution. But I shouldn't have assumed without testing! I'll try it out and report back.

I have a 18×24 sheet of plexiglass that I use to expose my images, and I've been doing two 8×10 cyanos and two 8×10 cupros in the same swoop. 5 minutes or so in bright sun, 12 or so in more cloudy conditions.

I wasn't specifically going for speed, although it makes the cuprotypes a lot more fun in my opinion. I'm just playing around, trying to get different visual effects with different chemical compositions. Developing cuprotypes in 10% ferricyanide pre-wash, for example, gives an interesting duotone effect (red highlights, blue lowlights). I'd really like to get a green somehow and feel like it might be possible with copper, but I restrict myself to pretty non-toxic chemicals. I know myself, and I know I will end up with chemical burns otherwise

 

[kaelynlayne]

Interesting finding. Congratulations!

I have some questions and suggestions in this context:

What is the improvement in speed that you obtained?

Is it possible to eliminate Thiosulphate completely or reduce it to the minimum amount absolutely required to get further speedup? The printout might not be strong after exposure but development in ferricyanide could make it stronger.

Would this also speedup Jim Patterson's Cuprotype process?

If speed is the main concern you may want to try @Cor's adaptation of Copper Printing process. It is at least as simple as hypo-cuprotype but much faster.

Have you tried varying the silver content, especially trying smaller amounts? The chemist in me wonders if the silver could be acting as a catalyst. In which case small amounts could be just as effective.

I haven't tried eliminating thiosulphate yet—I have the treated pages waiting, hopefully the sun will hold out today—but increasing the amount of silver nitrate speeds up printing time. Going from 1.2 to 1.3g 5% silver nitrate lessens the time to somewhere between a cyano and a VDB (3-4 minutes in bright sun).

No appreciable change to a developed print when placed in the sun.