In #coffee roasting the gases inside the beans expand dramatically. So much so the beans crack. They all do that around the same time during the process, so you get a lot of noise like corn popping.
You’ll usually log the first crack and work the roast from there. For specialty coffee light roasts you can start lowering your temperate there. The beans have a lot of thermal mass, so they won’t get cold instantly.
For a darker roast, you keep going past the second crack. Yes, there’s still enough action going on that you can get that popcorn reaction again.
Roasting is necessary - green coffee is hard and basically unusable, we’ve known that for ages. The choice of roast level is up to you though. A lighter roast will let you spot the differences between different origins. A darker roast will develop those chocolate notes many of us enjoy. A very dark roast will make higher and lower-grade coffee indistinguishable.
Thank you for coming to my TED talk.
With all that context, I’d just like to congratulate the manufacturers of supermarket-tier coffee for the outstanding innovations that allow them to roast coffee past the 50th crack. Between working in the industry and enjoy the hobby, I never thought you could go past the second. Yet here we are, drinking charcoal-water.