Hallo- I just JOINED this Venerable Site ! I love mixing my own ever since 1951 when the School Chemistry Master showed members of the School Photo-Soc how to mix up developers ! I tried this Formula today with some 1992 dated Kodak TMY 400 I downrated to 250ASA -- I mixed a x3 concentration, then I diluted it 1+3 with water -- was my maths corect as the test length of 120 film was severely under-developed at 10 minutes (guessed time) and I was careful to use 18oC not the usual 20oC. Regards to all the Experts on here, from Darkest Essex, England -- Peter.