Nothing new here for those familiar with this film-developing tank. I am consolidating a few tips dealt with elsewhere that may be useful for new users.

1. Follow Tim’s agitation routine on the 455 site’s developing demo video. The quick-flip and direction-reverse can make a big difference in evenness of development.

2. When developing a single sheet, insert the holder facing the tank wall. Agitation turbulence coming through the slots in the other, empty holder can cause a distinct extra-density pattern where the slots are.

3. Use the “squeeze play” given in instructions on the site. It really does prevent leaking. If you hear a slight “fizzing” noise during processing, it can be coming from air being sucked into the tank at either one of the caps or the O-ring. It is most likely the ring. See below.

4. You may wish to keep an extra O-ring or two on hand, a cheap way to avoid leaking. (They come individually sealed, so they won’t dry out.) I suggest periodically removing the ring and putting it back on so that the ends of the oval are now at the middle or along it. I also wipe mine with a bit of silicone spray every few months. These two measures, and replacement of the ring when they didn’t solve a problem, have led to trouble-free tank use. I once had a bizarre light-leak problem that neither Tim (inventor) nor I could figure out. Replacing the O-ring, though it appeared to be fine, solved the problem.

If you find that the top is not slipping on smoothly but causing a rubbing sound, you may also see the top not seating properly on one or both ends. The O-ring may be twisting. Try the first two measures together; change the ring if they don’t solve it, or just switch to a new ring.