I went away on holiday to Cornwall and shot some rolls of TMAX 100/400 in 35mm format, and some rolls of TRI-X and TMAX100 in 120 format. I've got brown stains on the 120 negatives in the densest parts and would like to get advice on what the remedy is. The rolls of 35mm have all been processed in the same drum, with the same chemicals as the 120. What is strange is that the 120 format film has some brown staining on a few of the negatives, whereas the 135 rolls are perfect. The rebate is clear. I'd like to understand whether this is dichroic fogging? I've mixed up fresh XTOL for the job, and have been using an older style Paterson screw lid tank for the job (actually branded Jessops but its the same kind), on both the 135 and 120 films, processing 2x 135 in a single drum, using 600ml of chemicals, and obviously a single 120 film using 500ml of chemicals. My processing was as follows: 1. XTOL 1:1, (no pre-soak), at 20.0deg+-0.3 using a Paterson thermometer which I have compared to another thermometer and its in agreement, 30s agitation followed by 3 inversions every 30s 2. Stop, reasonably fresh Fotospeed stop 1:19, 3 inversions, 20 degrees 3. Fixer #1, Fotospeed FX20, 75ml of fixer in 500ml of water, 20 degrees, 5 minutes, inverting 3 times every 30s 4. Fixer #2, Fotospeed FX20, 75ml of fixer in 500ml of water, 20 degrees, 5 minutes, inverting 3 times every 30s 5. HCA (1-year old but stored in 1L tanks topped up with Tetenal anitoxidant gas), 100ml in 500ml, 20 degrees, 2 minutes 6. Wash, using 500ml water at a time, Ilford type procedure, but until pink colour has gone from water, so typically 10-20 minutes of washing 7. 4 drops of mirasol, hang up to dry The staining is not immediately apparent when held up to window light, but on the light box, which is pure white to the side of the negative, it can definitely be seen that the negatives have a brown hue in the densest parts of the negatives, such as the sky. I read a John Sexton article on TMAX (dated 1987) that the brown stains can be dichroic fog which could be fixed using Farmers reducer for 30s. But I wonder whether this is simply some kind of optical effect which I have not noticed before due to the size of the negatives. This is the first time I have used 120 film, and goes to show it doesn't necessarily make sense to try something new for photos which cannot easily be taken again. On the other hand, this also provides some justification for going back to Cornwall, and I guess that its not really going to affect anything when I come to print which cannot be compensated for using different filtration.