I'd never used Farmer's or any reducer before this and I was impressed how just a tiny bit of brightening of the whites can change the overall "snap" in a print. Something to keep in mind for normal darkroom prints too
Even in the early days of salt and albumen prints, people published reducer formulas, so they must have thought it was useful. I never thought too much about it, and figured it was mostly to recover from overprinting, but reading through the threads about it here at photrio it's clear that some very good printers use it routinely.
Using thiourea as redeveloper also "feels" like it goes in the wrong direction... we've been pushing this process in a bit "safer", less hazardous, less toxic, less carcinogenic, less worry about disposal direction. I'm going to learn more about it.
For those two above, I made up the bleach fresh: about 150 ml 3% H2O2 with about 1.5 ml of 20% CA added. After the first one was done bleaching ( in close to normal time for me of about 40 minutes ) I poured it back into the plastic cup I'd mixed it in, and re-used it for the second one, where it finished bleaching quicker, after 20 or 25 minutes. The second one started out blacker with more developed silver, so that made sense.
But last weekend I tried to save some bleach and it didn't go well. For the first print, I made up 2 cupfuls using exactly the same plastic cup and squirts of CA... and it went as expected and it was nice to have deeper solution in the tray. There was about 1.5 cupfuls left in the H2O2 bottle, so I added 3 eyedroppers to that and then poured the 2 used cupfuls back into the bottle. The next 3 I tried with the saved bleach did not go well at all. All three of them took a long time ( hours ) and were much less light sensitive to the re-exposure ( I salvaged the last one by blasting it under my enlarger while it was sitting in the redeveloper, it took a lot of light to get it to reverse at all, and the darks are too weak ) and all of them have very stained highlights... beyond "coppery" and into "orange". The only thing I can think of is that the plastic funnel I used to get it back into the H2O2 bottle was not washed well enough... I use it for fixer, and I did rinse it, but maybe it had enough residual "something" on it to contaminate the bleach. And my earlier attempts to simplify the process by going straight from CA stop into the bleach also did not work well... the only consistent results have been with a good long wash before bleaching. The bleach is very sensitive to small changes in amount of CA or to contaminants carried over into it.
I think it IS possible that the tap water could matter. Maybe these things don't matter as much if you use strong H2O2, but I haven't tried that so I don't know.
I've got a backlog of paper negatives to develop now, which is great! Also 2 larger 7x11 negatives which I'm looking forward to developing. The best thing about all of this for me is that it got me back to making lots of pinhole paper negatives.... there were a couple years where I always had a coffee can or pinhole box in my car or when I went on a walk or when I went anywhere...I made one almost every day. It's fun and carefree and cheap and you can ALWAYS find something to make a picture of when you are just trying to make one picture... and it's fun to always have a backlog of negatives to look forward to seeing. If you're making them all the time, it's easier to experiment and try different things because it doesn't matter if it doesn't work.... a constant backdrop of something fun to do that makes life more enjoyable. So that's nothing to do with reversals, but I'm glad it got me going again.