Probably it's interesting to insert the text from Barry Thornton here, it was found at the end of his text on two bath developers. Here Kodalk is called sodium metaborate.(posted 8295 days ago)The Teaspoonful Two Bath
As far as I know nobody has mentioned another technique which I have evolved and which works really well to give different tonal characteristics and very similar automatic contrast control, and to avoid having to mix anything but an approximate Bath B – two heaped teaspoons of sodium metaborate in 1 litre of water. It dissolves almost instantly and is cheap enough to use once then throw away, though it would handle 15 roll films if re-used. Simply use your normal standard developer (T-Max, ID11, llfotech, HC110, Econotol, Perceptol etc.) for half to two thirds of the maker’s stated time as Bath A, drain it off, and use the teaspoon-measured Bath B for 3 minutes at the same temperature as Bath A. You may have to fine tune Bath A time by experience. For all 2 baths stop and fix afterwards in the usual way after Bath B, but not between the two baths