Uneven development

[Allan Reade]

I have recently started developing BW films, and my last film showed uneven development along one edge parallel to the length of the roll. On shots showing white foam from the sea, the edge of the frame was darker in positive, so under developed.
The film was Tri-X developed in ID11 1:1 @ 20 degrees for 11 minutes, the tank knocked when the developer was first poured in to dislodge air bubbles, then agitated for 10 secs every minute.
The camera was a Mamiya C3 with the correct lens hood for the lens used, so this isn't vignetting.
Any help greatly appreciated.

 

[user237428934]

Perhaps the tank was not full enough so that the upper part of the film was not completely in the developer?

 

[lawrence]

I have had exactly the same problem in M/F and I can make two recommendations (in addition to your current precaution to dislodge air bubbles and your agitation technique):
(1) Make sure that you have more than enough developer to cover the film. If the spiral is just covered with, say 500ml, then use at least 550ml, and (2) agitate continuously at the beginning of development for at least the first thirty seconds to ensure that all parts of the film have definitely been wetted (this will help to dislodge air bells in addition to rapping the tank).

 

[MartinP]

If your tank is one which can take more than one reel, then you might have to stop a single reel from moving up the centre-column during agitation, and therebye sitting partially above the developer etc. Some of the older plastic tanks needed a separate clip on the centre-column - in my experience the newer ones don't have (or need) the separate clips. For metal tanks I can't comment as I've not used them enough.

 

[Allan Reade]

Thank you for your replies. Increasing the quantity of developer slightly and making sure the reel has not slipped up the central tube sound very good suggestions. Thank you for your prompt responses, I will try this tonight. Allan.