We have equipment spanning from a small 200g sample roaster, used for sampling tiny portions of beans coming from our farms to make out the quality, to a 12kg Probat for very small production, usually for micro-lots of coffees and lastly our hot-air 60kg IMF Roaster. The latter outputs roughly 52kg of roasted coffee, since the beans in a roasting process looses weight due to water evaporation but gains in size, due to what is known a cracking, which expands the core of the beans similar to what you know from popcorn. Our 60kg is still refined enough that we can control every aspect of the roast and actually, the hot-air roasters are extremely good at ensuring a unison roast for all beans, since hot air has the ability to better evenly heat. The heat is coming from a holding chamber in the belly of the machine, fueled by a gas burner, which constantly keep the air in the holding tank at 650C. A blower creates the flow and an adjustable inlet controls how much of that air flows into the roasting drum to achieve the right profile. The drum rotates to stir the beans to further even the roast by subjecting them to equal measures of heat. The 12kg uses older techniques that some roasters still swear to, heating the drum itself. Think of it like comparing a hot-air oven to a traditional bottom heated oven.