After finally been able to find an enlarging frame to do 30x40cm prints, I was shocked that all my first attempts where spoiled by a creeping fog! The fog is really evident even in the safe lights at the edges where it starts, "creeps" a bit towards the inside and the rest of the paper has wave fog marks here and there. - I thought it was the safe lights. They were not. I tried printing without any of them (regular smal AP and Kaiser with red/orange filters, at safe distances) on in film tank loading conditions. - Maybe my new frame bounced the light? Nope. It is a high quality brand new LPL mask with black blades and dark ochre base. - The white walls? Nah. They are black around the enlarger and the effect of bounced light would not be so severe. - The trays? Brand new, 40x50. I thought of the labeling on the inside by a permanent marker, but I don't think it is that strong. - The paper? I tried my "older" 20x25 and 13x18 Ilford MGIV RC papers and all of them developed fog, even though my older prints (made in smaller 25x30 trays) were all fine. The fog was less for some reason in smaller sizes. - The enlarger? I developed two pieces of paper without light, a 30x40 and 13x18 and both showed fog. - The chemicals? All of them around 20C, Ilford MG dev, Ilfostop and Rapid Fixer and proper dillutions. I haven't tried dumping them and remixing to see if I made a mistake there because they are 2L each (great waste) but that could be it. Guys and gals, do you have any clues to help this poor man?