I recently tried my hand at deep tank development, with 30 rolls of HP5 in one batch, in 3-1/2 gallon tanks.
I followed the gist of the Ilford instruction contained in the Ilfotec HC data sheet, which state to completely lift the rack out of the developer solution three times, alternating direction of the tilt. This is much like sheet film.
Leery of the gushing of water through the sprocket holes, as I am with sheet film, I made my agitations very slowly...so slowly that I only did two per agitation cycle, and this took me 30 seconds each time.
I noticed that someone on APUG stated that Kodak recommends lifting the basket just a little bit to agitate, to prevent pump marks.
Well, even though I was extremely careful, I got pump marks on my 30 rolls. They are noticeable right on the negs, especially in areas of solid tone. I am hoping that some of them are salvageable, as they are all totally irreplaceable and very important to me.
What did I do wrong? I was more careful than Ilford recommend in their own data sheet.
Why are Ilford's and Kodak's recommendations so different?
I am, obviously, foolish for trying this for the first time with important film. However, I considered Ilford's instructions to be like gold, and have not had any problems with pump marks in the past, so I figured I was good to go.
Developer used was Ilfotec HC 1:63, film was HP5 Plus in 135-36 format.