How to agitate 'old' GAF tanks
Last year I bought my darkroom kit from a chap who was no longer interested. There were two GAF developing tanks in the lot. They date, at the least, from the early 1970s. They are small and black, only about a centimeter 'higher' than a 120 reel, and the top twists and locks on without being water tight.
A couple of days ago I decided to 'test' the reels with a short length of 120 and found that they wind on much more easily than my Paterson reels, so I have decided to give them a test. There is, however, one problem; they are not leakproof and when I turn them upside down for the 'Ilford' method, all of the fluid leaks out the sides!
So, what is the recommended technique for agitiating these tanks? How does one ensure proper circulation of chemistry without losing some off of the top and getting irregular development?