The following is a crop from an 8x10 contact print (please excuse the dust and crappy scan). I was determining how long to tone in "Kodak Professional Rapid Selenium Toner" for desired effect. I took 5 identical prints and toned for 1 minute to 5 minutes at 1 minute increments. Toner was diluted 1:5 with constant very light agitation. The prints were pre washed for 1 hour, toned, then washed again for 1 hour. I did not use a hypo clearing agent.
The first crop is from the print toned for 1 minute and there is no sign of any staining
This second one is from the print that was toned for 2 minutes. The red lines point to a change in image tone or contrast.
This strange tonal change was evident in the prints toned at 2 minutes, 3 minutes, and 5 minutes but not at 1 or 4 minutes. The problem was in almost the same spot on the 3 prints but not exactly. I know for sure that the 5 sheets of paper were pulled out of the package in sequence but once they were printed and washed I have no idea if they stayed in order and really doubt if they did. The paper is Ilford MGFB 11x14 and purchased new within the past month. Prints were developed in Dektol (brand new batch) stopped in used Kodak stop and fixed in fresh Kodak fix.
Contact printed using a sheet of standard framing glass. Light source was an enlarger using a cold light head and projected through an Ilford multi-grade #2.5 filter.
I am pretty sure this was not here before the toner, at least it was not evident enough to be noticed and I squeegeed the prints and dried them for about an hour and inspected them very closely before washing again and toning. The initial wash was only about 20 minutes and the wash before toning was 1 hour.