“C-26” was a partway success , setting the pH with a combination of Potash and sodium bicarbonate works well so far.
To be concrete:
2 g calgon
32 g potash
1.5 g sodium bicarbonate (has to be weigh out accurate!!)
3.5 g sulphite
1.7 g KBR
1.4 mg KJ
2.5 g HAS
5.2 g CD4
leads to a pH of about 10.12
Increasing the Potash to 33 g/Litre gave me a pH of 10.14/10.15 .
Because of working densitometer but rather “budget” ph meter with gel electrode, not approved for reductive photo chemicals, I do settle a measured ph of 10.14/15 at 25°C as my “aim”.
Here is the bad news: Increasing the KBR and the KJ leads to the wrong direction, although reducing the sulphite, I lost about 1/3 stop (0.05 D). Balance of the Colour curves is untouched and still very good.
Anyway, will use the residual “C-26” solution and do some more testing for slightly increased dev. Time and maybe again a prewash. The formulation is as close that I dare
“C-27” with (again) slightly reduced KBR / KJ and maybe slightly upscaled CD4 (with necessarily upscaled potash) will follow…
Regards from Germany,