Deeply Roasted

The first time I saw Daibo Katsuji roasting coffee felt like a profoundly religious experience. It was a spark of insight, a brilliant flash, and marked a bifurcation in my approach to roasting coffee at home.

Up until that point I had been using the SR540 air roaster Used by many home-roasters to produce light, uniform roasts typical of the origin-focused "third wave of coffee". with thermocouples and temperature-logging software. The curves looked good, and my light roasts were on par with the trendiest roasters in town. But it always felt like something was missing. Those acidic, tropical fruit juice-like brews smelled interesting and new, but never tasted deeply satisfying or comforting. Such coffee, it seemed, was unable to touch the soul.

To roast coffee, Daibo uses a steel drum, small enough to sit atop a portable gas burner. It's a beautiful manual process: the drum is rotated by hand, and the flame is moderated by adjusting an analog dial. There are no electronics involved. Judging the roast as it progresses is done purely with the senses. When I saw wisps of thick, almost blue smoke emerge from Daibo's drum I realized I was missing a key insight: the heat is fundamentally different.

Which is more appetizing, a steamed greyish steak that's cooked evenly throughout, or a fire-seared steak with caramelized crust, charred smoky fat, and a delightful cross-section gradient of doneness? That's the difference between convection and conduction.

Air roasters work by convection: they push hot air through coffee. The coffee is roasted very uniformly, but also surprisingly quickly. This is important for any roast, because you need strong heat to get the bean's closed fist-shape to pop open nicely and expose the inner surface area. After that "first crack", the bean is roasted for just a bit longer to allow what was exposed to catch up. Et voilà, you have a light roast, a gray steamed steak. Arguably as true to origin as can be without being raw, but such truth is not the same as how it is expressed.

If you keep roasting, eventually the bean's internal woody structure breaks down in a "second crack". Coffee oils are liberated, and migrate towards the surface where they start to get hot enough to break down into smoke. Just as in a fire-seared steak, fat and smoke in moderation creates inimitable flavor. But with an air roaster the only way to supply heat is to blow hot air, which immediately purges any smoke, and rapidly oxidizes and stales the oil that comes to the surface.

I started using the most primitive conduction roaster: a pan. The first pan I tried, a stainless steel one, quickly charred the coffee. A heavier iron wok stores and moderates the heat well, and makes it easier to stir larger amounts of coffee. But roasts take forever, and it isn't fun having to stir constantly for upwards of a half hour.

A lid brings outsize improvements: it creates an internal atmosphere that stores additional heat, providing supplemental convection which penetrates the entire bean surface. This speeds up development and enables efficient roasting of larger quantities of beans. A lid keeps the smoke and the flavor in, limiting fat-attacking oxygen. There are specialized coffee-roasting pots that come with improved lids that have a crank at the top, used to turn a paddle on the inside to agitate the coffee. However, I found that a portion of the beans were charred on one side, and another portion decidedly less developed than the rest. This is because rotating those paddles more or less just ends up sliding the whole mass of coffee around. They aren't really mixing or tumbling.

A metal drum, which is basically its own lid, solves this final problem by properly tumbling the coffee. Some of the smoke is let out from the small side opening, which is a very useful indicator on how the roast is progressing around the "second crack". The coffee oils and remaining smoke are combined thoroughly in the drum into a dark emulsion, which evenly coats the beans with a sheen like aged leather. Such deeply roasted coffee takes on a beautiful, handsome appearance. In A Daibo Coffee Manual (Nahoko Press, 2015), Daibo instructs us to look for this finish: to roast "to the point of smiling".

The superiority of the fire-conducting drum is clear, but perhaps most important is the ritual of turning it by hand. The roast commands your total and unwavering attention: if you stop, the coffee burns. You are wedded to the drum. Lose yourself in the rhythm of the coffee tumbling back and forth, and watch water vapor eventually transition into thick smoke. See the transformation from the beginning to the end, relying completely on your judgment. Access the rare vitality that comes with applying yourself fully and earnestly. Hand-roasting the Daibo way is a profoundly simple meditation, one that teaches the importance of living life in a wholehearted way.