Processing C-22 Film
C-22 is a colour negative process that preceded the current C-41. It was introduced around 1956 when Kodak released its next generation Kodacolor film. Kodacolor-X, the last consumer film produced by Kodak that used C-22, was discontinued in 1975. It can still be found as long expired unused rolls or as exposed film forgotten in old cameras or sitting in a cupboard for decades.
The C-22 process differs from C-41 in the type of colour couplers used in the emulsion, and consequently, in the chemistry of the processing solutions. Development was designed to be performed at 24°C, compared to 38°C required by the C-41. Processing times were longer and the emulsion was much softer, thus an extra hardening bath was required.
Not many specialized processing labs offer C-22 development these days, and even if they do the lead time would be months, as they would need to accumulate enough film to run a batch. It is possible to develop Kodacolor-X and other C-22 films in a modified low-temperature C-41 chemistry. This was tried successfully.
A further improvement could be achieved by using a Ferricyanide Bleach instead of C-41 Bleach/Fix, as suggested by Troy Walters. He developed at 20°C using the following procedure:
| Solution | Time, min |
|---|---|
| C-41 Colour developer | 20 |
| Wash | 4 |
| Chrome Alum Hardener | 4 |
| Wash | 4 |
| Ferricyanide Bleach | 6 |
| Wash | 5 |
| Ilford Rapid Fixer | 5 |
| Wash | 6 |
Troy does not mention using a stabilizer. I would consider adding a stabilizer bath as a final solution. It should contain formalin (or hexamine, which apparently decomposes to formaldehyde and ammonia in the solution). The method is very close to the original C-22 formula but has two important deviations:
- Benzyl Alcohol required to dissolve the couplers is missing
- The developing agent in C-41 is CD4 while the original process used CD3
Recreating C-22
The formulæ for C-22 were published in numerous issues of The British Journal of Photography Annuals and in Patrick Dignan's How to compound ... Simplified Color Processing Formulas. Most of the compounds required to prepare the solutions could be sourced from good photographic chemistry suppliers.
It might be possible to replace C-22 colour developer with that from the ECN-2 process. If the required amount of benzyl alcohol is added to the solution it becomes very close to the original formula. The details of the ECN process are published by Kodak in the Process ECN-2 Specifications. Grainy Vision blog post contains a wealth of information on preparing ECN-2 solutions and developing the film at home. Since the time it was published commercial ECN-2 kits became available from Bellini and Cinestill.
ECN-2 Colour Developer
The table below compares C-22 colour developer formula published in BJPA with that of ECN-2.
| Compound | C-22 | ECN-2 |
|---|---|---|
| Sodium tripolymetaphosphate | 2.0 g | - |
| Anti-calcium #4 | - | 2 ml |
| Benzyl alcohol | 5.0 ml | - |
| Sodium metaborate (cryst.) | 85.0 g | - |
| Sodium carbonate (anhydr.) | - | 25.6 g |
| Sodium bicarbonate | - | 2.7 g |
| Sodium sulphite (anhydr.) | 2.0 g | 2.0 g |
| Potassium bromide | 1.6 g | - |
| Sodium bromide | - | 1.2 g |
| CD3 | 5.3 g | 4.0 g |
| Kodak AF-2000 (optional) | - | 5 ml |
Here and below, all amounts are to make 1 litre of the working solution.
The main difference is the absence of Benzyl Alcohol in ECN-2, higher concentration of CD3 in C-22 and the use of different accelerators. Kodak AF-2000 is an anti-fogging agent, which might or might not be present in the commercial ECN-2 kits. Otherwise, the two formulas are essentially equivalent.
C-22 films are developed for 13 minutes at 24 °C, while ECN-2 only takes 3 minutes at 41 °C. When using the ECN-2 colour developer in C-22 process it should be possible to use 13 minutes as a starting point and adjust it as required.
Stop Bath
The stop bath consists of 20 ml of glacial acetic acid and 10.0 g of anhydrous sodium sulphite. Given a long development time a thorough wash could probably be used instead.
Hardener
The original formula used Formalin as a hardening agent. According to PhotoEngineer:
Formalin reacted with the leftover coupler and also the gelatin to form substances that resisted both coupler induced degradation and the bug attacks.
Thus, Formalin served as a hardener, coupler stabilizer and biocide. For that reason, it is recommended to use the original formula for the hardening solution:
| Compound | Amount |
|---|---|
| Formalin | 20.0 ml |
| Sodium carbonate (anhydrous) | 10.0 g |
If formalin is unavailable, Chrome Alum hardener can be used instead, for example Agfa 406
| Compound | Amount, g |
|---|---|
| Chrome Alum | 15.0 |
| Potassium metabisulphite | 15.0 |
Or Kodak SB-3 which consists in 30 g of Potassium Chrome Alum to make 1 L of solution.
Ferricyanide Bleach
The C-22 bleach formula is given in BJPA:
| Component | Amount, g |
|---|---|
| Potassium nitrate (crystalline) | 25.0 |
| Potassium ferricyanide | 20.0 |
| Potassium bromide | 8.0 |
| Boric acid | 5.0 |
| Disodium tetraborate | 1.0 |
It is noted that a faster-acting E3/E4 bleach can also be used, the composition of which is as follows:
| Component | Amount, g |
|---|---|
| Potassium ferricyanide | 112.0 |
| Potassium bromide | 24.0 |
| Disodium hydrogen orthophosphate (dodecahydrate) | 62.0 |
| Monosodium dihydrogen orthophosphate (anhydrous) | 15.6 |
| Sodium thiocyanate | 10.0 |
Fixer
C-22 fixer consists of 120 g of ammonium thiosulphate (crystalline) and 20 g of potassium metabisulphite. Any rapid fixer should work equally well.
Procedure
The standard C-22 procedure includes eight steps:
| Solution | Duration, min | Temperature, °C |
|---|---|---|
| Colour developer | 13 | 23.9 ± 0.3 |
| Stop bath | 4 | 20.0 - 24.4 |
| Hardener | 4 | 20.0 - 24.4 |
| Wash | 4 | 20.0 - 24.4 |
| Bleach | 6 | 20.0 - 24.4 |
| Wash | 4 | 20.0 - 24.4 |
| Fixer | 8 | 20.0 - 24.4 |
| Final Wash | 8 | 20.0 - 24.4 |
Agitation should be continuous for the first 15 seconds, then for 5 seconds every 30 seconds.
References
- Processing KODAK Motion Picture Films, Module 7. Process ECN-2 Specifications. Eastman Kodak Company. 2020 (PDF)
- Kodak Publication J-1. Processing Chemicals and Formulas for Black-and-White Photography. 1977 (PDF)
- Patrick Dignan. How to compound ... Simplified Color Processing Formulas. (PDF)
- The British Journal of Photography Annual 1981, pages 198-201 (PDF) and 205-206 (PDF)
- C-41 processing early 1950s Kodak Kodacolor films
- Shooting/processing vintage 40s-60s era Kodak colour film: Part 1 Kodacolor
- Shooting/processing vintage 40s-60s era Kodak colour film: Part 3 Ektacolor