Why cast iron?
Our 3kg (five gallon) cast iron roaster with our custom made 10kg cooling bin.
Over the years, the second most common question we get asked (after “Where do you get your beans?”) is “Do you really roast in a cast iron skillet?” The fact is, we think coffee roasted using the flat bed cast iron method simply tastes better than coffees roasted in other ways. Here, I’ll break down a little of the science of it.
There are two ways to apply heat to roast coffee beans. (These are the same for any cooking or heat transferring process, but we’ll focus on the coffee here.) During convection roasting, the coffee is heated and cooked through the circulation of hot air inside the roaster. Air fryers use convection heating to cook food. Conduction roasting, by contrast, is the direct transfer of heat between two objects that are in contact.
Traditional drum coffee roasters heat the air inside a bean-filled spinning drum, made of either cast iron or stainless steel. Convection accounts for at least 70% of heat transfer in a drum roaster, with the rest via conduction through beans coming in contact with one another or with the drum itself. A relatively new and less expensive style of coffee roaster, called fluid bed roasters, almost completely use convection heat transfer to both roast and keep the beans in motion, all in a contained steel hopper.
The Iron Skillet Coffee flat bed cast iron roasting method uses conduction heat almost exclusively. Heat is applied directly to the cast iron which in turn transfers heat directly to the beans. As the temperature of the beans rise, they become heat sources themselves, aiding in driving the roasting process forward.
(Convection heat transfer does happen during cast iron roasting. Natural convection occurs when the hot air rises, and we use that principal keep the roastery clear of smoke by pulling the smoke, and therefore the rising hot air, out of the roastery via our venting system.)
Cast iron is an excellent conductor of heat for roasting coffee because it does not retain heat. Instead, cast iron passes heat directly to the bean. The result is coffee that is bold, original, and rich with depth and character. From the juicy and bold African beans, to the dense and complex Central and South American beans, to the delicate Indian Malabar, Iron Skillet Coffee creates rich, flavorful coffee from the first sip to the last drop.
For us, coffee is not about the quantity that we can produce in any given batch, but about the quality of the coffee that comes out of every batch we roast. That’s the Iron Skillet Coffee difference.
