Some exciting results!
I finally have a developer that can be used as a concentrate with 1+19 dilution (i.e., it's a 20x concentrate).
Compared to XTOL, it has: Lower contrast, same grain, very slightly better shadow-detail, same sharpness. In fact, I want lower contrast because I often shoot in contrasty situations, such as sun/shade, or harsh indoor lighting.
I took PE's hint that the path to better image-quality means longer dev-times, so I reduced the alkali some, yielding this concentrate which produces 1 liter of working solution:
Propylene glycol ................. 39 ml
Ascorbic acid ..................... 10.7 g
Sodium metaborate ............. 6.5 g
Phenidone .......................... 0.15
Propylene glycol to ............. 50 ml (you should only need to add about 1 ml)
I poured all the chemicals into the PG at the same time, instead of waiting for them to dissolve separately. It took about 30 minutes of constant stirring at 50C to get everything to dissolve. Jerry suggests letting the brew sit overnight at room temperature, and that it'll all eventually dissolve without heating. I did this last week and it worked, but this time I was impatient.
If I continue with this, I'll need to get a hot-plate/magnetic-stirrer combo.
To use, you must separately add 90 g/L of sodium sulfite to the distilled/deionized water first so it'll scavenge oxygen, and then add the concentrate. If sulfite is measured volumetrically (and thus less accurately), then the same graduate can be used for both sulfite and concentrate, because the user will measure powder first, then liquid.
Target pH is somewhere around 7.8-7.9 (I need a pH-meter!). Add 15% to XTOL's times, because this developer is similar to XTOL as it uses the same chemicals in similar proportions.
It has no chelating agents, so I suspect it can only be reliably used with distilled/deionized water, and I still wouldn't trust a working solution that's over a few hours old.
Why is the contrast lower?
I'll speculate that this developer has poor (nonexistent?) buffering because I removed the boric acid, and that causes the pH to drop more in dense areas, hindering development more in dense areas. That is, the poor buffering is causing compensation. Or am I off in the weeds about this?
Other comments or criticisms about this developer?
I know that to make this into a product, we'd want to incorporate a halide-solvent into the concentrate in order to eliminate the separate sulfite, and that lots of testing would be needed. I remember that Ryuji discovered a couple of films that worked poorly with his DS-10. That sort of knowledge only comes from thorough testing.
I enjoy this...