Let me begin by quoting Ansel Adams on the subject of developers and development:
“Perhaps no art, science, or craft has evolved by such an extraordinary combination of pure science, pure witchcraft, and wishful thinking as that which constitutes the popularly accepted procedures in photography. In the development processes above all others, weird mumbo-jumbo persists and flourishes.”
The advent of digital photography at the expense of chemistry has perhaps blunted Ansel’s words somewhat, but those of us who still practice the dark art of chemically developing film and prints will know there’s always more to learn about that basic process of developing a latent image into a thing of beauty to behold. Well, if it’s worthwhile that is. If it’s a well-planned and executed photograph in which care was taken before the shutter was pressed with the eventual image in mind, then the chances of it being worthwhile is increased and the risk of failure decreased. That is one aspect that both chemical and digital photography have in common.
Anyone who has processed film in chemicals, in particular B&W films, knows that the developing chemical can usually be diluted. The most common dilutions are 1:1 and 1:3. Thus there are three main chemical strengths that can be used: Full strength, dilution using 1 part stock solution with 1 part water, which doubles the available volume of solution, and dilution using 1 part stock solution with 3 parts water which quadruples the available volume of solution.
When full-strength solution is used each film processed will reduce the strength of the solution such that a calculation has to be made to extend the developing time for each successive film. Unless notes are carefully kept this method becomes somewhat hit-and-miss, with the strength of the developer towards the end of the given number of films that can be developed (even allowing for calculated extended development times), becoming suspect. An alternative is to add a replenisher to the developer after each film developed in order to maintain the strength of the developing agents.
It’s therefore better to dilute the chemical and use it as “one-shot” for each film development. This ensures the strength of the developer being constant for each film developed without the need to re-calculate an extended development time for subsequent films. As the term implies, “one-shot” means the developer chemical is discarded after each film developed.
Diluting the developer at a ratio of 1:1 or 1:3 also means extending the time the film is in the developing solution. The time for a dilution at 1:1 is longer than full-strength solution, and for 1:3 longer again. This ensures the developing agents activate the silver halides to the same extent as for full-strength solution. This also means the developer can be extended by dilution and more films developed for a given volume of fluid, right? Wrong! The following shows how the volume of the developing tank associated with the total number of films that can be developed using full-strength solution determines the dilution ratio.
The photo here shows one of the tanks I use for developing 4”x5” sheet film. I’ve stuck labels on the outside of the tank indicating the volume to use for inversion agitation or rotation. This tank is designed for use with the Jobo processor with the tank rotating on its side, so I use the rotation method. This allows a lower volume of chemical, in this case 270ml. If I employed the inversion method I’d be using 560ml of chemical.
You’ll also notice the rubber bands wrapped vertically around the tank. This is simply my way of indicating there is film in the tank waiting for development, so don’t remove the rubber bands and take the lid off! It’s simply the KISS principle.
What, then, should the dilution be if I didn’t want to use full-strength solution requiring constant and subsequent re-calculation of the developing time?
The first clue is printed on the packet the dry chemical powders came in, in this example Ilford ID-11. The packet required mixing to obtain a 1 litre stock solution, and the data indicated this would allow development of 40 sheets of 4” x 5” film. The tank I use provides for six sheets to be developed in each process, thus a total of 42 (6 sheets times 7 development sessions) sheets so this is the number I use in my calculations and it’s only marginally over the indicated 40 sheets.
The major factor determining the right dilution isn’t using dilution to develop more film, but how many films the chemical is designed to develop. The next major factor is the volume to be used in the developing tank.
So, you might ask, if the information on the packet of developing powder states the developer can be diluted to a maximum 1:3, why not just dilute 1:3 which gives the greatest overall volume, then use 270ml of the diluted fluid for the developing tank? After all, development is extended to compensate for the lesser strength of the fluid. It would allow a total of 4 x 40 sheets of film to be developed (160 instead of 40) and a good cost saving to boot. Unfortunately that line of thought is folly.
The information on the packet is quite specific in that the developer is designed to develop 40 sheets of film. What isn’t stated is this means whether the developer is diluted or not!
Fortunately it’s easy to calculate the correct dilution for the volume to be used in the developing tank. In my case I divide the 1,000ml of stock solution by 42 to get the proper developer strength for each developing session, which is 142.9ml. I round this to 143ml. It can be seen this is roughly half the 270ml volume needed for rotation development, therefore a dilution of 1:1 gives me 280ml of solution. On this basis, a dilution of 1:3 means the developing action is exhausted too early and the resulting negatives would be “thinner” and under-developed. This might confuse photographers who felt that using the 1:3 dilution was acceptable, and lead them to incorrectly suspect under-exposure of the film was the problem.
A similar exercise is followed for inversion development. In the case of the tank illustrated this requires 560ml of solution. Allowing that 143ml of developer is the correct amount to develop 6 sheets, then 143ml of stock solution to 3 parts water, or 429ml, produces a solution total of 572ml. Thus rounding to 140ml of stock solution and 420ml of water gives 560ml of developing solution – spot on. The slight reduction in stock solution from 143ml to 140ml has negligible impact on the final results; similarly the extra 2 sheets of 4”x5” film in the equation won’t affect the overall results. I normally give slightly more time for development so this would compensate for the slightly greater dilution of developer.
I also use Paterson tanks for developing 35mm and 120 rollfilm. The following gives the calculations for 35mm (36-shot) film in the Paterson single-film and double-film tanks:
Single film tank: This takes 290ml of solution, so the first thing to establish is how much developer per film. The packet says 1 litre of stock solution is suitable for 10 rolls of 36 exposures, the same for 10 rolls of 120 rollfilm. This makes the calculation easy. 1 film = 100ml of stock developer solution. The tank, however, is close to 300ml so neither 200ml (1:1) or 400ml (1:3) suits the tank capacity. The closest is 1:2 to make 300ml. That then is the correct dilution. The packet says develop at full strength for 8.5 minutes, dilution 1:1 for 11 minutes and dilution 1:3 for 20 minutes. Plotting the data on a piece of graph paper indicates roughly 15 minutes development at dilution 1:2, so that’s what should be used.
2Double film tank: The tank says 290ml per film, thus volume for developing 2 films is 580ml. Let’s say 600ml. Two films means 200ml of developer, thus 1:2 ratio, or 200ml of developer plus 400ml of water, gives the 600ml needed. To be honest, 200ml of developer plus 380ml of water would yield a negligible difference to the slightly more dilute 600ml of fluid because the same quantity of stock developer is used.
Whilst developer can be diluted, Stop Bath and Fixer must be used at full strength.