Quote Originally Posted by Gerald C Koch View Post
A T-grain developer is one that is specifically formulated to work with T-grain emulsions such as Ilford Delta and Kodak Tmax.
Delta emulsions are core-shell technology, not T-grain. Kodak uses T grains.

That aside, referring to developers in a way that implies they're "for" these specific emulsion types, and conversely implying they're "not for" cubic grain emulsions, is neither standard practice nor wise. Any black and white film developer can be used with any black and white negative film. Results from various combinations thereof range from very bad to excellent, irrespective of what the developer is called or was allegedly intended for. Trying them out is the only way to determine suitability of negatives for a given purpose/taste.

Kodak screwed up when naming its TMAX and TMAX-RS developers. As a result, people have been confused ever since.