Since I live up in the arctic, a lot of my photography includes snow and winter landscapes. When making darkroom prints, it bugs me that I can’t seem to get a good cool tone in the prints. Toners like sepia and selenium give the opposite of what I want to achieve, which is a more cyan/blue tone. Gold toner does work well sometimes, but it is just so very expensive nowadays so I am not using it other than for particular larger fiber prints I want to mount and frame.
Since I have a bunch of benzotriazole and I know that restrainers will give cooler tones, I tried it on a bunch of tests and found that 1-4ml/l gave absolutely no visible difference. I didn’t go further than that, but I am sure that at about 10ml/l you will get some cooler tones, based on internet hearsay.
But I knew that Wolfgang Moersch has a product called Finisher Blue which is supposedly an additive that you can use with your regular developer to get a more cold tone developer. Based on the MSDS I could see that it contains, as to be expected, mostly BZT, but also something called 1-phenyltetrazole-5-thiol. Or Phenyltetrazole/Phenylmercaptotetrazole. This is also a restrainer, and I found a mention of it in a patent by Polaroid from the 80s. I contacted Mr Moersch about this additive, if there was any difference with using it or just regular BZT. He said:
Finisher Blue contains a much stronger and more bluish working restrainer Phenylmercaptotetrazole.
So, while it contains just two different restrainers, according to Mr Moersch, this other one is more blue working. Sounds hopeful!
The instructions say to use 5-10ml per liter of developer, and Wolfgang mentioned that after 3ml the paper will need more exposure to get to the same level of density. I can confirm this, already at 4ml I needed to add about half a stop of light more. In these example images I tried to keep the average brightness the same but it was difficult. Here are examples of 0, 4 and 8ml per liter of developer. I used Moersch Eco 4812, which is already a slow acting developer and with this additive it got even slower. I recommend starting with a slightly spicier than usual developer to adjust.
At 8ml it took probably 10min to develop the sheet, which I think introduced some green tones. As you can see below, it almost looks like the 4ml one is cooler than the 8ml.
The difference is slight and subtle, but it is there for sure. Without a good monitor, you might not even see a difference, but in real life you can see the cooler tone.
The shot above is printed on Ilford MG IV RC, and here below you can see how different paper reacts to Finisher Blue. The Foma RC paper I also tried got an even cooler tone and reacted in my opinion better. The cool blacks feel nice and black, with the Ilford paper it feels like something is a bit off. Something got funky with the contrast, and I was struggling to get a good filter/exposure time combination.
Both these tests are extremely non-scientific. Not only is the exposure different in each sheet, the scanning process will introduce variables too. I set black and white points for each channel on each image, and tried to make them look close to the real life paper, but I can’t say I spent a lot of time trying to match anything. I just wanted to get some examples and let you guys know a product like this exists and how it works.
Lastly, what is a restrainer? Well - a restrainer will increase the threshold when a silver crystal that got exposed to some amount of light, gets developed by the developer. So you could say it acts like a high-pass filter on the emulsion. These are often used to prevent fogging. All light sensitive material will get exposed to some degree by microscopic amounts of lights or cosmic rays, but you don’t want them all to get developed, only the ones that you intended to get developed. The chemistry behind this all is complicated, but you can add a restrainer when working with fogged material to reduce the fog. However, I would say it is not worth it when trying to salvage paper. Especially multigrade paper. Even if you get rid of the fogging, there is just something really off with the contrast and the tones. It will always look kinda dull and weak.
If you have any toner/additive hints on how I can achieve cold or blue tones in my prints, please write a comment! I would really like to know how master printers go about achieving them.