Tasting the coffees that I roasted yesterday for my next class. We're doing brewed pots of coffee first because that's going to be safer for everybody and second because we're dealing with roasting plans for production roasts and most people don't drink their coffee one spoon at a time out of a cupping bowl.
The 2nd flight might be the most difficult one for students. It's taking the lightest coffee from the first flight and doing two variations where the total time in the roaster is a minute less, but in one that's all front loaded where there isn't significant chemistry happening in the coffee and in the other it's divided proportionally through the entire roast so it looks the same in the percentage breakdowns.. There's a larger, but still subtle difference there.
The fourth flight takes the darkest coffee from the first flight and adds variations where all the batches have the same total roasting time and match up to the start of first crack, but one goes faster through first crack and slower through second crack while the other goes slower through first crack and faster through second crack. Here again there are some clear differences in flavor.
For these very dark roasts, most students tend to prefer the roast that looks like an S curve (get the coffee hot enough to get your dark roast flavor characteristics fast enough that you're not overly diminishing flavors developed earlier) and I suspect that will continue to be true this time around.