Fog solved After months of going slightly crazy with my roll film showing fog, from either my magazines or the darkroom I stumbled on the answer.. I have fluorescents lights in the darkroom because it is tiny with a low overhead. I tried incandescent but the heat in the summer nearly drove me out in 5 minutes. A week or so ago I was still looking for answers and was checking with a black light. Low and behold the my RC focusing sheet on the enlarger glowed like a torch! Being a bit of a neat nut I would setup with a nice clean white sheet sitting there under the tank and reels innocently. Once I started using my print inspection light for set up and no RC paper near the loading all the problems disappeared ..Who knew the stuff absorbed and gave off UV? The clue should have been that the fog showed a pattern similar to the stainless steel reels which were partially blocking the UV Live and learn.