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The Quest for a Bigger Batch.

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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.

The Weber Genesis: open full-size image in new window

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…

The heart of the machine: open full-size image in new window

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.

Inside the drum: open full-size image in new window

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.

Cooling the roast: open full-size image in new window

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.

Jessie, the RoastMaster: open full-size image in new window

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. ;)

Author: deCadmus

Doug Cadmus is a usability guy, writer and sometime dramatist who moved to Vermont for the coffee, where he's the Web Guy for Green Mountain Coffee Roasters. When not writing, reading, or tapping out haiku-like Twitter posts, he roasts coffee in his garage.

8 Comments

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  2. Hi Doug,
    I like the roaster you’ve created. I have a similar one in mind. My question is about the roasting process in the drum. How do you know what it’s doing? Are you using a thermometer to assist your burner adjustments?
    I’m currently using a Stir Crazy and Heat gun so I can see and hear whats going on.
    If I understand your ramping up you go from medium to 3/4 at 6 minutes and to full heat at 12 minutes…right?
    Thanks,
    -=Greg=-

  3. Hi, Greg.

    Two thermometers, actually. In the case of the Weber grill, the built-in thermo provides a decent “rough guess” of where the temperature is. Much better is a temp probe inserted smack into the mass of beans tumbling in the drum, but that can prove a bit of an engineering challenge. Were I still actively roasting on the Weber I’d certainly have picked up a laser targeting infrared thermometer to aid my efforts. (And because they’re really cool!)

    So far as the temp ramping goes, your understanding is spot on.

  4. Hi,
    random question. I noticed that you have my exact grill. Weber two burner older model. Someone gave this to me last year and it is still running strong but needs a new propane tank. I bought a tank and a new hose / regulator for it and it won’t fit on my grill. It looks to be about a half inch connection where it connects to the weber but the hose that is already on the grill connects to a smaller conncetion (maybe an eight inch). Anyways, just not really sure what to do and saw your post and noticed you had the same grill and was wondering if you ever had to change your connection and what you did. THanks
    Eli

    • I found an adapter, a brass fitting, which couples the old and the new configurations of propane cylinders. It screws inside the fitting on the cylinder, and adapts to the quick-disconnect fitting of the grill. If memory serves, I picked it up in the seasonal / grilling aisle at my local Home Depot.

  5. Hey man, thanks so much! Found one at my local ace and my grill is burning for the first time in months. Thanks again!

  6. Hi, Doug,
    I came across your website in a very round about way via Sweet Maria’s to homeroaster.com and was intrigued by your link there. I have the same generation Genesis grill, but 3-burner one, that is still going strong after 10 yrs (with some parts replaced). Very interested in trying my hand at roasting my own beans “cheaply”. The questions I have about your home made roasting drum are: 1) is there much equipment required?
    2) how did you secure the “fins”, the mounting bracket on the open end and the wire basket to the trash can?
    3) your photo appears to show the standard Weber rotisserie motor, from your use, how much beans can it handle? 1lb? Less?
    4) the wire basket, those look like standard kitchen colander baskets?
    5) about roasting temperatures, you wrote that you started at “medium” on both burners, do you know what tempt that is? with my 3 burner one I’m guessing “medium” may run hotter than the 2 burner version (but then I could turn off the middle burner and leave the front and back ones on). Would be good to know rough temp ranges.
    The reasons for the many questions is because we don’t have many tools at home, but if provided with clear instructions on what is needed I can probably get my hubby to do this for me :-) Appreciate your time and response!

    • O dear. I’ve been away for a bit and so failed to respond more timely-like. But respond I will.

      1) It depends. Coffee roasting can be as simple an effort as you want it to be, or as complex.
      2) Rivets where possible, and screws where I felt I’d want to be able to break something down later (for cleaning, etc.)
      3) I found the standard Web rotisserie motor is more than capable of a pound of coffee. It stands to reason; I think it’s likely that folks might presume to roast a 3 pound chicken on this kit.
      4) Yup!
      5) Medium on my two-burner Weber would do about 400 F. Your mileage may vary — a lot! I’d try to find a temperature path to complete a roast cycle in 18-20 minutes.

      Overall, I had pretty darn good luck roasting with the Weber, but I ultimately gave it up for a dedicated drum roaster so that I might more reliably repeat a particular roast. If repeatability isn’t a tremendous issue for you, it may be just the kit you’re looking for.

      Have fun!

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