This post examines the normal development time for my home-made Rodinal in a 1:25 dilution.

In my first post of this series I explained the process for testing my home-made Rodinal developer with Ilford HP5 35mm film. I found that 10 minutes, or something very slightly shy of this, was appropriate for developing HP5 at box speed (400 ISO). Later I looked at the massive dev website for typical Rodinal times and found that 11 minutes was listed against commercial Rodinal for box speed at 20C. So my version is not that far out from the commercial stuff – (10%).

I decided to use the remaining undeveloped negatives from that test for looking at Rodinal at a dilution of 1:25, another standard for me.

I guesstimated a time of 5:45 minutes going on the massive dev ratio between 1:50 and 1:25 dilution at ISO of 400 of 10/11. I could not get the temperature down to 20C, it being a very warm day, so I shaved a further 10% off the time to compensate for the additional 1C that I had. So my development time at 21C was 5 minutes, rounding very slightly. This is getting close to the lower limit of developing times that I operate with; anything shorter and it becomes difficult to have a consistent process for pouring in and out time and agitation. At these short times small differences in technique can bring about large effects.

Here is a scan of the print from Rodinal 1:25 on the new Ilford Portfolio RC paper compared to Rodinal 1:50:

Scan from print: HP5 Rodinal 1:25
Scan from print: HP5 Rodinal 1:50

As you would expect the print from Rodinal 1:25 has more contrast as there is less compensation, but the two are quite close.


This confirms that my home-made Rodinal is working well. The development times are quite close to published times and the differences between 1:25 and 1:50 are as I would predict them to be:

  • More contrast but printable on grade 3
  • Less grain in the shadows.

My next post will be about finding a personal time for HP5/Rodinal. However, as these tests show,my personal speed is not far off box speed.

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