Developing Film

Following on from my last blog, regarding my use of Ilford PQ Universal developer (and it's clones), I should perhaps expand upon the reasons why I use the dilution of 1+29.  As I mentioned in the previous blog the dilution of 1+29 allows similar development times to ID-11/D76.  Why is this important?

Firstly dilution. What does 1+29 mean?  With tools like the Massive Dev Chart app, it is easy to use the instructions given to make the development solution. The instructions state that 16.7ml of Developer is added to 483.3ml of plain water at 20 degrees centigrade. The total making 500ml of developing solution; This being the correct amount of developing solution for a roll of 120 film. Easy right?

Well yes and no. the 1+29 means the following;

1 part developer

29 parts water.

To find the correct amount of developer from this the following arithmetic is used.

1+29 = 30

500/30 = 16.7 (the / means divide and the 500 is the amount of developing solution used in milliliters).

The one part is now found in our formula 1+29

To find the 29 parts simply multiply 1 part by 29

16.7*29=483.3 (* means multiply)

so 16.7+483.3=500

Measuring fractions of a milliliter is impossible, and quite frankly unnecessary. I measure 17ml of developer and top up with water to the half liter.

17+483=500ml.

The time taken for development is critical, up to a point. The Massive Dev Chart app will provide timings for particular films. For example it states that when developing Kentmere 400 in PQ Universal, the development time should be 8 minutes and 15 seconds. Individual timings are unimportant here but any developer and timing that is used should be greater than 5 minutes and less than 10 minutes, as a guideline.

Why should the time be longer than 5 minutes? There are two reasons why this might be so.

• The ratio of neat developer to water to make up the developer solution that will be used, will be higher and there is more chance of uneven development on the resulting negative.
• The timing will be too short to guarantee consistency; A small mistake in timing, for example starting your timer late, can have a large detrimental effect on the negative.

It is worth noting that the above points apply to processing film by hand in a Paterson tank or similar.  Machine developing has been designed to allow short development times, normal contrast and lower dilutions of chemicals.

It is also worth noting that the standard developer, ID-11/D76 from Ilford and Kodak respectively, have timings that are between 7 and 9 minutes, for development using a stock solution, that, in general, is the recommended way .  This is no coincidence! These timings allow for better consistency in negative development by ordinary people. Shorter or longer timings require experience and a well practiced technique.

So to sum up, the importance of a dilution of 1+29 allows timings of between 7 and 9 minutes, or thereabouts, which mitigates any inconsistencies in technique and produces beautiful negatives of a standard contrast.

Image taken on TMAX 400 film and developed in PQ Universal 1+29.