I recently set asside some time to work on cuprotypes using Frank Gorga's recipe toned with the complex toner. This is a short report on my experience.
Collecting Materials
All chemicals were puchased at ArtCraft who have been super helpful, total cost probably came out to around $40 with enough to make probably 100 prints. The limiting item and the most expensive was potassium ferricyanide.
Time To D-max
First I worked on finding the minimum time for d-max. This demonstrated an interesting quality of cuprotype: It has an extremely long tone scale into the blacks.
I baked this step wedge for 100 minutes, and while it's hard to see from the picture, there is a small tonal gradation between every single step in the wedge! Unlike other printing methods where d-max was somewhat obvious, with cuprotype I found I had to make an artistic decision that balanced exposure time and the density range of my printer.
I also experienced some small issues with d-max consistency. In the example below the top print was exposed for 100min and the bottom was exposed for 25min but the bottom print is less than 2 stops less dense. I believe the difference was in the coating. In the more dense print it took me more time to get a smooth coat and so the print ended up absorbing more sensitizer from my brush.
[Note: I posted this experience report on photrio.com and received the feedback that for cuprotype it's better to expose for the highlights which given this very long toe makes sense to me]
Printing
I started by printing a negative with Christina Anderson's salted paper curve. In the process I was taught for making curves we always applied the curve as the top most layer in photoshop, but Christina Anderson actually applies the curve then inverts and so my first attempt was wildly wrong, but this is a good lesson. In any case after fixing the negative I made a couple of test strips one at 25 minutes and 35 minutes respectively.
I split the difference at 30 minutes and made a print.
This further highlights the inconsistent d-max. I find this print to be too dark for my taste, and maybe a good half stop or more darker than the 20min test strip. Again I think this has everything to do with how much work I had to do to the paper to get proper coating. When coating the small strips I was able to do minimal passes with the brush for an even coat, but when scaled up to a full 8x10 size I needed more time with the page and with brush coating I believe that resulted in more sensitizer being absorbed by the paper.
In the end I guessed at 20 min and tried again for my final print.
I think this print turned out lovely. It's sharp with a nice long tonal scale, the color is lovely and fits the subject well. If I make more I'll adjust the curve slightly to bring up the shadows, there's more details back in those shadows that are being crushed in the final print, but I don't think it's a big enough detail to print a new negative for.
Conclussion
Cuprotype was a fun side quest. It's a method with a lot to love and some downsides. The color, tonal scale, sharpness, and cost are all excellent, and make it a method that's worth exploring further. However the time to print and wash and tone and wash makes for a very slow process, and one that's difficult to refine with such a long iteration cycle. I'd love to spend some time making a better curve that fixes the crushed shadows but I don't think I want to spend the amount of time needed. I think that if I tried it again I would look into the addition of silver nitrate to accelerate exposure as well as some of the other recipees and toners that might offer speedier printing.