Ian Grant
Subscriber
DK76 is claimed (on Digital Truth, and in some book I have somewhere) to be equal to D76. I don't think it's more active. Instead of 2g/L Borax, it's 2g/L sodium metaborate. But I haven't tried it. I could make it and see, I guess. But I still probably wouldn't notice. Who cares about fine grain? Use bigger film.
Kodak possibly doesn't recommend dilutions higher than 1:1 because of minimum recommendations of stock/roll. You can't fit 250ml of stock in a 500ml tank if the dilution is greater than 1:1.
Borax has a pH pf 9.5, Sodium Metaborate is pH 10.5, that's a very significant difference in alkalinity, so activity. Crabtree & Henn mention this increased activity when the formulae were first published in research papers.
Remember that Sodium Metaborate is formed by adding Borax and Sodium Hydroxide.
Ian