I suggest you get Ilford's Fact Sheet on the Delta Films. (See http://www.ilford.com/html/us_english/bw.html.) I use Delta 100 for about half of my work. Most of the other half is made up by Delta 400 (the rest is Delta 3200 [seldom] and quite a few Kodak b&w Infra Red films). For all the Deltas, I found Ilfotec HC to be a fine developer.(posted 8770 days ago)For the Delta 100, it's the 1+31 dilution for 6 minutes at 20 0C (or 68 F), four inversions at the beginning of each minute that gives me good results. Ilfotec HC is a one-shot developer with a fabulous shelf life. It comes as a thick syrup-like liquid which, however, can be conveniently and accurately dosed using a syringe. If you don't like the syrup, try Ilford's LC 29, which is said to be an amateur version of Ilfotec HC, and comes in smaller quantities.