Sunday, September 20, 2015

Theory and praxis

Below you may see 2 photos, one in color and another in B&W. The first photo was exposed in a Clack camera, using Fuji Superia 100 expired 1998. The second was exposed in a Pentax MZ-60 using TMax-400 expired 2000.

In common they have the expired date but they have more in common: they were developed simoultaneously in the same tank with the same developer. Both were developed for 30 minutes, then rinsed and fixed. After this the B&W was taken off from the tank and putted to wash and the color film underwent a blix process to remove remaining silver and finally washed together with its 'black brother'. And then both were hanged to dry.

I made some changes to the recipe I gave in the last post and, like expected, it worked well, I might have to reduce developing time from 30 to 20 minutes because both looked a bit overdeveloped.

3 g Potassium Metabisulfite
20 g soluble coffee
6 g CD4
30 g Potassium Carbonate
1.3 g Potassium Bromide
Water to make one liter
Use at 20ºC, agitation first 30s then 10s each minute for 20 minutes

Saturday, September 19, 2015

A multipurpose developer

I've been long looking for a film developer that could be used both for color and black and white films. I have not yet the final formula but it will not take too long anymore to establish it.

If you are following this blog since its beginning, you will remember that I started developing color films with a very simple homemade soup which included only CD4, coffee and sodium carbonate. I succeeded but having to adjust colors and it was a one-shot thing you had to prepare each time, so not practical.

Then I started using Dignan's 2-bath developer (at room temperature) and I made several changes and experiments with the second bath in order to achieve better results. This was quite a long enterprise.

In a recent discussion with a net good fellow we came to the conclusion that color films may be developed in a one-bath developer at any lower temperature than the recommended by brands, if we only adjust the times. At 20ºC it takes about 20 minutes and the results are very good.

If you read this recent article of mine, you will understand how I discovered that coffee can replace an important agent used in C-41 developers called HAS (Hydroxylamine Sulfate). And having in account the several variants of the formulas of a C-41 developer, I composed following recipe:
3 g Potassium Metabisulfite
1,2 g Potassium Bromide
5 g CD4
10 g Coffee
25 g Potassium Carbonate
Water to make 1 liter
 This recipe has a lower amount of Carbonate for pH reasons and takes slightly more time, about 30 minutes to develop a C-41 film at 20ºC.

I made a 500ml batch of the recipe above and it developed several C-41 films in a time interval of about 2 months but now I think it is becoming weak and I will have to prepare another. Neverthless, I exposed the day before yesterday a B&W film and, after estimation of the developing time with a stripe of the same film, I gave it a try developing for 90 minutes. And it did develop the film satisfactory.

It would be much better if the development times for color and B&W were the same, but B&W is taking about the double of time. So, the next step is to prepare a new soup with twice the amount of coffee and adjusting Carbonate to get the same pH as the previous recipe, about 11.

If I succeed to have a developer that develops both color and B&W in the same time, I can imagine that it will be possible to load a developing tank with color and B&W films and develop them together. But, attention, B&W can't be bleached, only fixed. So, the procedure would be following:
  1. Developer - X minutes
  2. Rinse or stop bath
  3. Rapid Fixer - 3-5 minutes
  4. Open the tank, take the B&W film out and put it in water to wash for 30 minutes
  5. Blix the C-41 film to remove remaining silver and filter layers - 15 minutes
  6. Wash C-41 for 15 minutes
  7. Hang both films to dry

Long expired TMax400 developed in Caffenol-color