Quaker. From under-ripen beans:
Charring. From too hot of heating surface:
Tipping. Again from high heat of roasting surface or in my case, the drum rotation is too slow:
Center line charring. From too much heat from drying phase to 1st crack:
Crater. Generally due to too much heat from 1st crack to 2nd crack:
Under roasting. The bean just finished 1st crack. Notice the approximate 90-degree angle from the flat surface of the bean to the semi-circular bottom. Good for cupping, not so good for daily drinking:
More drinkable roast. Bean expansion after 1st crack. Notice the rounding of the previously mentioned angle:
Bean expansion after 1st crack, from a different angle. The center line is not charred, and the silver skin is evident: