Fully Analog B&W Trichromes

Time to take my proof of concept for analog trichromes to the next level.

I shot these photos on an expired roll of Ilford Delta 400. It was about 20 years expired, and I metered at 200ASA. I didn't change the development time at all, under the assumption that overexposure alone would be sufficient to get good negatives.

The initial digitally-made trichrome, for
reference.

Scans of the three negatives I'm using, from left to right: Red filter, green filter, blue filter.

This process is simple enough to create on a computer, but I wanted the challenge of creating a fully-analog color photograph. This particular roll of film gave me trouble printing because it still had a tendency to curl even after drying. But the result was good enough as a proof of concept.

For printing with cyanotypes, the RED filter is used for the CYAN layer, the GREEN filter is used for the MAGENTA layer, and the BLUE filter is used for the YELLOW layer.

The yellow layer came first, and the exposure seemed good. All details were clear. This layer was exposed for 120 minutes.

The magenta layer, in this case using cuprotype instead of cyanotype, developed a little stronger than I wanted, overpowering the yellow quite a bit. The exposure time for cuprotype is much longer than for cyanotype, so I think I can reduce the exposure time by a fair amount, hopefully at the same time increasing contrast. I did mess up the alignment here though, my bad... This layer was exposed for 60 minutes.

The final cyan layer was the trickiest to balance. Too much exposure and the cyan is way overpowering. I think I got pretty close here but the magenta/red is still very strong. This layer was exposed for 40 minutes.

Overall it's pretty obvious that the magenta/red layer completely overpowers the print. The pure white (or light grey) on the front of the cap is far too red. But aside from alignment issues, I'm pretty happy with how this turned out. At least it proves the concept, and leaves room to make adjustments for the next attempts.

Trichrome Cyanotypes

Hopefully those reading this have seen my previous post about my Bicolor Cyanotype technique. Calling this next step "Tricolor Cyanotype" is a little misleading, because one of the color layers is in fact not cyanotype at all, but rather cuprotype. I've found that other attempts at creating a red layer don't satisfy my "purist" view on creating a fully analog process, or at least one that can be recreated using easily-obtained raw materials.

The chemistry of cuprotypes is similar to that of cyanotypes, where a solution of copper ions reacts to ultraviolet light similar to how an iron solution is used for cyanotypes. The chemistry is remarkably similar too, with ferric ammonium citrate comprising one part of the cuprotype mixture, the other part being copper sulfate. I use a third component, thiourea, but this is not strictly necessary when making cuprotypes. There are many resources available online to learn about cuprotypes, so I won't describe the process here.

Exposure for this technique is a little tricky, as the magenta/red (cuprotype) layer can very easily overpower the other two layers. Additionally, too much exposure on the final cyanotype layer can completely destroy the pretty green tones from the mix with the yellow layer. In general, exposure for the cyan layer is roughly one-third the exposure for the yellow layer. I'm experimenting with exposure for the magenta layer, the exposure above I believe was roughly equal to the exposure for the yellow layer.

Another post will follow soon where I use this technique to make a trichrome print from negatives.

Bi-Color Cyanotype Experiments

I was recently inspired by bi-color cyanotypes I saw online, and wanted to take a crack at the process myself. I started simply with solid colors rather than printing with negatives, as the testing process would probably be very long for the latter. I first wanted to see what this process is capable of.

Since I'm sure everyone is familiar with how cyanotypes are made, I won't describe the process in detail. The yellow layer in bi-color cyanotypes come from bleaching a blue cyanotype with sodium carbonate (washing soda). I use 1 tsp sodium carbonate to 1 L hot water, and bleach the cyanotype to completion. My first tests were to determine how much exposure was needed to achieve a satisfactorily yellow layer.

I expose my cyanotypes using a DIY exposure box, lined with UV LED strips. The UV intensity in this box is rather low, so my exposure times tend to be longer. However, I can achieve much greater consistency using my exposure box than relying on sunlight.

From left to right, the exposure times are 30m, 60m, and 90m. Not a huge difference between the three prints at this stage.

The same prints, but fully bleached with sodium carbonate. Despite the initial prints having very similar values of blue, here it's apparent that the overall exposure during the blue step makes a big difference in the yellow value.

On each bleached print I coated another cyanotype layer and exposed all three for 30 minutes. I reduced this exposure time for later prints, but it's still easy to see that the darkest yellow combines best with the blue layer to make green. The fact that the blue and green aren't too different in value makes the prints feel a little flat.

Here is a later print that I'm happy with, with the blue layer receiving less exposure than the prints above. The exposure may have been on the light side, but the color separation is much cleaner:

I have more experiments I'd like to attempt with this technique, so stay tuned for more soon.