There's a multitude of emulsions available, even after a lot of them have been discontinued. Each one reacts a little differently to light, both in terms of requiring more or less light, but also in terms of reacting in various unique ways to light.
I'm going to write out a proper entry about my exploration of IR film as part of my series black and white and how I explore it. But I'm in the midst of information to share, so I'm going to share my thoughts and news now and worry about writing out a proper chronology of exploration later.