In recent months I have been having serious issues with a purple/blue stain remaining on my Ilford FP4 sheet film, after processing in Perceptol developer. I posted some examples of this on my blog some time ago. I have had similar issues with other films in this developer. I had a number of theories on what might have been causing the problem. It is obvious that it is the anti-halation dye of the sheet film that is not fully washing out during processing.
At one point it was suggested to me that perhaps because the film was stored frozen, the anti-halation dye of the film was being affected. I tried some fresh, unfrozen film, and it was better, but the problem did not fully disappear. I also tried a stronger developer solution, but that didn't help either.
I process my sheet film with stainless steel hangers in open tanks, obviously in total darkness. I usually run a rack of six or seven hangers at a time. Over a number of batches it became apparent that the outside sheets in those batches had less of a staining issue, than the ones that were grouped in the middle.
On February 5th I processed a batch of FP4 in Perceptol, in my Jobo Processor. This processor uses light proof tanks in a temperature controlled water bath. The agitation is continuous, with a motor that rotates the tank. I find that the continuous agitation does not provide quite as nice a tonality as the minimal agitation of the hanger method, so I don't use the processor all that often.
This batch of FP4 came out flawlessly, with absolutely no stain. Obviously the agitation with this developer is of critical importance in order to fully wash out the dye. Now I just have to fine tune my development time to give me the best possible tonality. This method also has the added benefit of using less chemistry.
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