Hi, I did quite a bit of B&W reversal a couple of years ago, using the Ilford method, but have had a lapse until recently. I've just processed a roll of HP5+ which I found I had exposed but not developed. It was of some night shots of an oil refinery. They've turned out quite nicely but there is an issue with a few of the frames where there are dark vertical streaks (the gaps between the streaks corresponding with the perforations in the film). Could any of you experts shed any light on which part of the process I am making an error in which might have caused this? I use distilled water for all solutions, for the first washes after first development, and for the final rinse, but tap water for the other washes. I'd be most grateful if someone could shed some light on this. There are also a couple of frames where there are what look like other bits of emulsion swirling but not in the above pattern, although as they're long exposures and there was steam etc coming out of the refinery equipment it's quite hard to distinguish steam from development problems!!