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Sunday, June 22, 2014

C-41 for everyone

I am involved with B&W Photography since I was about 14 years old. I knew its workflow, from film to print, but I was unable to understand the Chemistry involved, nor I mastered all the details from the capture until a ready print.

Now that I am over 60, I have more time for Photography and I could turn real a dream I always had, to develop color negatives. When I started, I even didn't know that the chemical process of color negative films was called C-41. And I still don't know where the name C-41 comes from. Maybe Color Process number 41, or 4 baths plus 1, doesn't matter...

My first step in what C-41 is concerned, was to buy a developing kit and follow the steps indicated in its brochure. The process is very demanding in what temperatures and times are concerned and it was established for automatic processing, for sure. Not for people doing C-41 in a simple developer tank, I think. But some people seem to like following very strict instructions and they do C-41 according to the standard instructions.

I am sure that, if C-41 had been established for home processing, it would be very different. I am going to try to explain the standard procedure, then you will realize how difficult it is to achieve always the same quality. Of course, this standardization was needed because C-41 films could be developed anywhere and, contrary to B&W, the colors must be the same, disregarding where you let the film be developed. In B&W, the film can be developed with more or less contrast, with more or less grain, a little over or underdeveloped. That could always be repaired at printing. But a color film must have the same quality everywhere.

Standard C-41 process:

Development - 3' 15" at 38,5ºC

Rinse - 3 times, very quickly
Bleach - 4' 00"
Rinse - 3 times
Rapid Fixer - 3' 00"
Washing - 30', flowing water
Stabilizer - 1' 00"

All baths should be at 38,5 ºC. Crucial is the temperature and time of the developer. Manual control is almost impossible, variations will occur if you do not use a thermostatic device. The 3' 15" developing time are also important and this causes stress and not plaisure like it should.

Now, about the chemicals involved:

The developer contains, as developing agent, CD-4, a p-Phenylenediamine derivative, Hydroxylamine Sulfate as stabilizer and Sodium Carbonate as alkali. CD4 is a silver developer that by its oxidation provides the dye components needed to form the color image on the film. It seems impossible to replace CD4 with another developing agent, so far. If a C-41 is developed with a B&W developer, for instance, only silver will be developed. If the film is bleached, all the silver will be transformed back to halides and washed out by the fixer.

The Bleach Bath, in which ferric-EDTA is mainly used, is necessary to remove the silver without washing out the dyes. The Bleach transforms silver in halides and the fixer solves them and on the film we have then only an image formed by three dyes, Cyan, Magent and Yellow.

The fixer removes the halides from the film. After fixing, the film should be very well washed to remove completely the fixer and finally the film undergoes a 1 minute stabilizer bath to protect the organic dyes against deterioration. This bath is a very diluted solution of formaldehyde.

Finally the Fixer, it is the same used for B&W films. And there are mainly two choices: Sodium Thiosulfate based fixer or Ammonium Thiosulfate based fixer, the only difference is that Ammonium Thiosulfate acts faster, 2 to 4 minutes against 10-15 minutes for Sodium Thiosulfate.

OK, if you want to follow this strict instructions, it is up to you. But I have been working in a room temperature process, based on the Dignan's 2-bath C-41 process, to which I added some own experience in order to get better colors. I have been using Dignan's process alone but I was not fully satisfied with the results:

The two younger
Photo 1 - Developed with Dignan's 2-bath C-41 process

Yes, we get 'color' but they are not 100% correct. Of course it is possible to make corrections via Software, but it would be better not to have to, to use the pictures like they are scanned, with minor changes in the automatic scanner settings.

I reproduce here Dignan's recipe, for 1 liter of both baths:

Bath A

600 ml distilled water
1 g Sodium Bisulfite
11 g CD4
9 g Sodium Sulfite Anhydrous
Water to make 1 Liter

Bath B

500 ml distilled or filtered water
45 g Sodium Carbonate (monohydrate), aka washing soda
1 g Potasium Bromide
Water to make 1 Liter

Bleach and Fix are the usual for C-41.

The main difference is tath all baths are at room temperature and you mussn't care about some seconds more or less. On the other hand, you don't need Hydroxilamine Sulfate as CD4 stabilizer. Each time you use the bath A, the quantity will diminished of say, 20 ml. One liter is theorectical enough for 50 rolls, unless bath A goes bad before.

I have tried to warm bath B (where development takes place), and I found out that this improves the colors. But then, I measured the pH before warming and after warming and it was clear that the warm bath had a higher pH. This showed me that, instead of warming the bath, we may achieve the same result by increasing its pH. So I decided to add some Sodium Hydroxide to Bath B and the colors shifted to a much better approach to the real colors.

City Walk
Photo 2 - Developed with Dignan's 2-bath process at higher pH

And here are the recipes I have used:

Bath A

600 ml distilled water
1 g Potassium Metabisulfite
11 g CD4
9 g Sodium Sulfite
Water to make 1 Liter

Bath B

500 ml distilled water
50 g Sodium Carbonate anhydrous
1 g Potassium Bromide
5 ml of a 10% Solution (10g for 100ml) of Sodium Hydroxide
Water to make 1 Liter

In bath A, I am using Potassium Metabisulfite instead of Sodium Bisulfite because it is easier for me to buy at local stores and it does the same as Bisulfite. It is added as first as Oxygen scavenger to prevent the Oxydation of CD4 when this one is dissolved in the water. Finally Sulfite will act as preservative of the solution, whose pH should be 6,5 or less.

In Bath B I use 50g of Sodium Carbonate anhydrous and not 45g of monohydrate because I use a 5% solution for other B&W developers and this doesn't change the result and keeps pH after use, it may be reused several times. The small amount of Sodium Hydroxide, 0,5g/L, provides a change of the pH from 11,6 to 11,8 or 12.

I have learned, by my own experience, that the paper of an alkali in a developer is somehow similar to its paper as washing powder for tissues.The alkali soaks and softens the film in order to allow the penetration of the developer in the layers of the film. Using Dignan's process alone was not developing well the red color in prints that corresponds to the cyan layer which is at the bottom of the film. With a higher pH, this layer (and the others) gets well developed.

Daily walk
Photo 3 - All 3 colors Blue, Green and Red well represented

To finish this long article, let us see how you may develop your C-41 films.

Prepare 1 Liter of bath A and divide in 2 bottles, each one of 500ml. Mark one as the work solution and the other as replenishment. Each time you develop or each 2 or 3 times, fill the work solution with the replenishment.

Prepare only 500 ml of bath B. This bath is not 'consumed' because it receives water from the previous rinse bath, balancing what it loses when leaving the tank.

Prepare also a 500 ml bleach bath for C-41 and 500 ml Fixer. Personaly I prefere the so called Blix bath, Bleach and Fixer in one bath only. This bath will last very long, you only need to filter it from time to time. Keep it in a amber bottle because it may be affected by light but leave the bottle open, it needs air for long life, It is not wrong to through it from a bottle to another several times to aerate. The recipe for Blix may be found here.

C-41 at room temperature
Photo 4 - This is all you need to process your C-41 films at room temperature

And the workflow can be this one:

- Pour Bath A into the developing tank and agitate for 1 minute and give some taps on the work bench with it to free the film from possible air bubbles.
- After 10 minutes pour the bath A back to its bottle.
- Pour Bath B into the tank without rinsing or washing.
- Use semi-stand development with bath B, 1 minute constant agitation and then 3 gentle inversions or rotations per minute.
- After other 10 minutes, pour the bath B back to its bottle.
- Rinse very well 3 times with water
- Pour BLIX into the tank also for 10 minutes.
- Wash very well and hang the film to dry.

Note: I am not using the stabilizer bath, because the stuff (Formaldeyde) is not very healty and I prefer to wash very well and accept that my negatives will not keep forever. Me too!

Important: Please check latest recipes for the 2.nd bath of 2-bath developer that proved to be better.Here:


Anonymous said...

Holy smokes...this is awesome. thanks.

Chris Zahller said...

Are you saying that Bath 2 is a 10-minute bath with inversions during minutes 2 through 10? That's a lot of agitation & a short time for so-called semi-stand. Not questioning your results, just the terminology.

Henrique Sousa said...

In fact it is! The more we agitate in bath B, the less grain we get. A rotary tank would be ideal.
Thanks for commenting here.