From what I've read, Stoeckler, Thornton and Adams (likely many others also) experimented with variations on Kodak D23. I use the Adams variant of D23 which is 7.5/100/1litre for A and 10/1litre for B. I'm using "20 mule team" borax for the B bath and it works fine. I also presoak for two minutes and my films are FP4+ and PlusXAero in 4x5 and 8x10. This (the D23) stuff lasts forever. I'm currently using 8 month old D23 and it's working fine. My times for PlusXAero rated at iso10 are 5 minutes in A and four minutes in B. It's been a while for FP4+, so I don't remember now, but 4+4 rated at iso100 come to mindThe late Barry Thornton reformulated Stoeckler's Two Bath recipe for thinner modern films. Comments on this?