Ilford Rapidfix, to be precise. Diluted 1+4. Here, let me tell you the story.
So I mixed up this present batch on 4/15 (I write down the date, but not the number of rolls I process. I've found that during a normal shooting schedule for me, fixer lasts about 1 month, at which point I check it with HypoCheck after every use and discard it when I see a precipitate). Today being almost exactly a month after that date, I decided I'd HypoCheck it after today's use. But as I poured it into the tank, there was a lot of weird, white, relatively large (though >1mm diameter) flakey precipitate at the end of the pour. I thought that meant that it was spent, so I left it in the tank for 8 minutes instead of my normal 6, and then instead of discarding it outright, I HypoChecked it. And you know what? It came out clean! No precipitate! By the by, when I poured it out of the tank post-fixing into a pitcher to HypoCheck it, there was no more precipitate, although there was a quite beautiful colloid of tiny tiny barely-noticeable particles.
Never having seen this before, but remembering that the Tetenal C41 instructions mentioned that if there's a precipitate in the blix to heat it up gently until it's gone, but also not knowing how much heat Ilford Rapidfix can stand, I took the risk and put the pitcher of fix into a hot water bath (110F) and left it there for a couple of minutes and then stirred it well. Colloid gone.
So now I decide to rinse out the brown plastic bottle that the fixer was in, in case there's more precipitate in it. What comes out? Pure black water! Well, just lots of black powder dissolved in water. It's exactly what I see when I rinse off remjet from Fuji 500T. But I did not process any film with remjet in this fixer.
My questions:
1. WTF?
2. Am I correct in assuming that the fixer is not spent, due to it passing the hypocheck test, and that gently heating it to dissolve the colloid didn't affect it?
3. Seriously, WTF??
4. What was that black precipitate in the bottle?
5. No really. WTF???