The problem is Amidol doesn't keep well in solution, nor does Glycin. Ilford worked on a Phenidone - Glcin concentrated developer but in commercial production it had poor shelf life.
Meritol the combination of PPD - Pyrocatechin has been used and had a better shelf life
I'm about to give up on a Metol analog of Rodinal. I could more easily concoct a Metol-C-TEA. I have a compound of Metol and C in glycerin. I call it a compound becuse it seems to be more than a solution. It has 2.5 grams of Metol and 4 grams of ascorbic acid in 100 ml, and took 250 F to get it there. Now I'm out of Metol, but have more p-aminophenol coming tomorrow. I don't like the idea of using KOH, mostly because it's hard to tell what I'm getting when I weigh it because it turns into a puddle while I weigh it. I probably should have made a solution as soon as I opened the container, or else sprung for the money to get it in the solution form. I'm going to see what happens when I use K2CO3 to form the potassium aminophenolate. The CO2 should fizz away for the most part with a little help from heating. We'll see. If that doesn't work, I'll see what I can do with K2CO3 and Ca(OH)2, which will at least make a solution of KOH and a limestone rock I can use as an ornament.
Ian -- I was under the impression that glycin didn't keep well in powder form (note Photographers' Formulary's comment on glycin that it has a limited shelf life), but that when it was in solution it would remain stable and active for quite a while, even if it did darken.
Glycin caused keeping problems for both Ilford & Paterson developers, but you could use it where shelf life isless important. The importance of Rpdinal is the very long shelf life etc.
Glycin keeps well in solution, but keeping worsens as pH goes up. It is quite stable in a 2 part developer. Amidol keeps poorly in solution at any pH unless one adds certain stabilzing agents.
That's what all the hip lab cats do, man.
Tetenal seem to know how to make metol based developer of high pH that keeps well, see the msds for Neofin Blue in the thread on High Acutance Developer.But they are not likely to spill the beans on how it works.
It's the simplicity of Rodinal combined with the quality of the negatives produced that lead people like Patrick in search of similar developers using different developing agents.
But in a 100+ years it's been copied by many other companies, including Ilford & Kodak but no-one has yet come up with a simple alternative using other developing agents, that keeps well as a single solution concentrate.
This is why Rodinal is so remarkable.