Originally Posted by jstraw
From your first post, I've taken it that you are using 2-bath fixing, that is, a first tank followed by a second tank. Since the first tank collects most of the silver, I call it the "dirty" tank. The second tank, with a relatively small amount of silver, I call the "clean" tank. (In the industry, the normal nomenclature would be "fix-1" and "fix-2").
The reason I suggest checking the silver content of the final fix tank (the "dirty" tank, fix-2,etc.), is that you normally want to keep this below a certain spec concentration. If you look for "exhaustion" in the first fix bath, you really don't know much about the silver concentration in the final fix tank. It depends largely on how much solution carryover you have; this is the amount of solution the wet film or paper takes along with it. If you don't use squeeges between all the tanks, you probably can't "exhaust" the first fix bath before the second bath exceeds fairly low silver limits.