Lately I have been enjoying a lot of bw reversal processing. The last stage is still fix, as there are still small bits of undeveloped silver to be removed. In a perfect world, all remaining silver would be developed in the 2nd developer. Ordinarily exhaustion due to silver levels would dictate when the fix is done. I would imagine that it would be more likely spill over that would kill it now. How would I know when it is done? Is it a question of testing Ph?