My body of roasting experience can't compare with most roasters on this
list, and I'm on my third IR; one IR1 and two IR2s. In the beginning, I
relied on roasting with a thermocouple and had excellent results after
about my fifth roast. When I received my last IR2, I decided on relying
on senses alone and think I'm getting the hang of it by intense
observation of the process (i.e., OC mode).
The profile I'm using is 1) 350d / 3 minutes, 2) 370d / 3 minutes, 3)
390d / 3 minutes, 4) 405-410d / 3 minutes, 5) 435-450d / 3 minutes.
Note-taking includes the time when the beans go through their various
changes in colour (light green, tan, cinnamon, and various shades of
brown), rate of colour change, rate of expansion in the chamber, etc.
On most roasts of 5.15 - 5.35 oz., when the bean mass reaches 3/4 to 7/8
up the roast chamber collar 1st crack will soon follow. Then the beans
really begin to expand, darken and expel the parchment from the beans
and depending on the bean, chaff flow may (again depending on the bean)
increase. By the time the beans are touching the bottom of the
mushroom, the roast should be nearing the end. Once the beans are
between the collar top and the mushroom bottom, start thinking about
when to force a cool-down. Taken to a deep dark brown, lacking any oil
spots at all, and when the beans are at or just beyond the bottom of the
mushroom seems to me to be FC to FC+.
Since I only drink drip or French Press for the moment, I try to never
go past that point. Depending on the bean, sometimes things get
exothermic and the roast wants to rush into 2nd, but not too often if
one is careful.
Much babble here, but it works for me. BTW, I sure am glad I have 4# of
Bug left in my stash.
Good luck to you IR folks.