Posted on November 24, 2002 - by deCadmus

The Quest for a Bigger Batch.

Sooner or later it happens. You’ve been roasting for a while… sharing with family and friends. Maybe you’ve just bought a new espresso setup, and suddenly discovered the voracious appetite that your portafilter has for fresh-roasted beans. And it hits you…. Your air roaster, even tweaked to double its roast volume, just isn’t enough. It’s time to upgrade.

So where do you go from here?

The options don’t look good. Commercial sample roasters can roast a pound or more at a time… but at $4000 to $7000 for the privilege, they’re pretty much out of reach [of your author, anyway.] The Alpenrost? At $300 its price is more down-to-earth than the sample roasters, but its eight ounce capacity offers precious little more roast volume than an air-roaster. Is there no way to achieve a 1 pound capacity at thrifty prices? Sure there is… build your own!

If you’re anything like me, chances are you have the makings of a suitable coffee roaster right in your own back yard. In my case, there happens to be an LP gas-fired Weber grill sitting just outside my back door… a two-burner model that’s sold these days as the Genesis A model.

This is Weber’s smaller, two-burner model. Even so, it’s rated at 22,000 BTU, more than capable of roasting a pound of beans. A further bonus: Weber has a full line of accessories for its grills, including a very sturdy rotisserie [model 9890]. On, then, to the heart of the device…

There’s a fair number of things to be considered when choosing materials for a roasting drum… and stainless steel makes short work of virtually all of them. It’s food-safe, able to handle wild temperature swings, and provided it’s fashioned heavily enough, it can take just about whatever abuse you might dish out. For my purposes, a perforated, stainless wastebasket was just the ticket. That’s right… I’m roasting coffee in a trash can. ;)

To mount the drum, I fashioned a bracket for the “open” end of the can out of 1/4 inch aluminum stock… easy enough to shape, and sturdy enough to stay put. To bolster the “closed” end, I used an off-the-shelf electrical fitting. I added brass “fins” to help lift and agitate the coffee beans, which otherwise would simply scoot along the bottom of the roasting drum en masse. Finally, to make it easy to dump the beans at the end of the roast, I attached a funnel-shaped wire basket at the opening, and cut away the wire mesh at the bottom of the basket.

A peek inside the business end [left] shows the wire-basket funnel, the aluminum bracket mounted to the rotisserie’s skewer, and green coffee beans tumbling over the brass fins inside. This photo was taken at the very beginning of the roast.

On the whole, the setup works exceptionally well… and provides a good deal more control than a simple air roaster. I can fully control the temperature throughout the roast, and quickly learned that I would need to. Too much heat, too early in the roast leads to less-than-uniform results. [The salt and pepper result of that particular roast was quite tasty, but I suspect that was merely good fortune... not a method to rely on.] Likewise, not providing enough heat at the critical stages ramping up to first and second crack could easily stall the roast.

Ramping is an operative word. You’ve got to build some momentum to coax a pound of green coffee beans from room temperature to pyrolysis, especially if you don’t want to scorch a few beans along the way. Through trial and error I’ve learned that, with an overall roast time of about twenty minutes, I’ll get solid results if I start the roast with both of the Weber’s burners at “medium” and raise them to “high” through two intervals… the first at about six minutes into the roast, the second at twelve minutes.

Depending on the bean, first crack will begin about 18 minutes into the roast… second around 22 minutes. And don’t forget, it takes some concentrated airflow to cool a pound of just-roasted beans. A “turbo-bladed” fan and a wire basket can make short work of it.

Is it worth the effort? Absolutely. It’d be worthwhile if only to be able to roast greater volumes of coffee in a shorter timeframe. To my delight, I’ve found the flavor of the coffees I roast has improved as well. Acidity, in particular, cups brighter with this drum setup than with my tweaked air-roaster, though perhaps not as bright as the Freshroast, which is a good thing, in my view. Many coffees seem to finish slightly sweeter, as well… but maybe that’s just wishful thinking. ;)