This
That is why I didn't want to give up. My bottle is probably two years old, but I bought it because I believed it to last a long, long time. It is hugely popular so must work, but I don't want to keep wasting good film. My budget is very much a shoestring. Part of me wants to bin it and stick with developers I trust, but another part doesn't want to waste £10 worth of developer. Is my process correct? Should I swirl it before use? Should I agitate every 30secs? Should I approach the MDC with a degree of scepticism? What does ring-a-round mean?
Ring-a-round refers to developing a bunch of film at different times, and then picking the time that results in negatives that match your needs.
Small tanks, lots of small lengths of film, and lots of patience and time are necessary.
It is a term that makes a bit more sense in the context of printing times, but it still works.
This site dealing with Assessing Negatives shows a very detailed ring-a-round:
https://www.ephotozine.com/article/assessing-negatives-4682
From that site:
You just need to attach development data to each box.
Short bulk loads of film - say 6 frames each - or a 135-36 roll cut into 5-6 strips of properly exposed identical frames. To make for good tests the subject should have a wide range of tones and be illuminated by diffused but directional light that results in clear shadows and distinct highlights.
And you should absolutely approach the MDC with skepticism - it is a useful resource, but erratic in reliability.