After trying fresh roasted coffee, I've been hooked and was determined to learn how to do this myself. I'm an industrial designer and at some point I'd like to design and build a cool coffee roaster for myself but before I get there, I've been learning the basics and came up with a method that works extremely well, requires no fabrication skills, uses an off the shelf roasting basket, a cordless drill and a few items found in a typical workshop. Below is a quick video showing the general process of roasting some coffee. Follow the steps to learn how to start roasting your own coffee!
Step 1: Assemble the Roaster
The nice thing with this roaster is that you don't really have to fabricate anything. Just some simple assembly. The heart of the roaster is the basket to hold the beans. At this point I didn't want to re-invent the wheel so I looked for something I could buy off the shelf and found that the basket for the Behmor 1600 home coffee roaster is available as a separate part. The one I bought is actually an older version that was on clearance for only 10 bucks! However, the newer version has a smaller hole pattern in the mesh and will allow you to roast smaller beans. I'd recommend spending the extra bucks on the new version as I do get some beans that fall through from time to time, so it does limit your been choices a bit. The Behmor basket is nice because it has a round slotted shaft on one end which fits on a BBQ rotisserie bracket and on the other end it has a 1/4 inch square shaft that just happens to fit a 1/4" socket wrench adapter.
I purchased my basket as well as different varieties of green coffee beans from Sweet Maria's.https://www.sweetmarias.com/product/behmor-small-grid-drum
Next you'll need to assemble some sort of drive shaft out of whatever parts that will allow you to attach your cordless drill to the roasting basket. I started digging around in my toolbox and found a 1/4" to 3/8" socket wrench adapter, fitted to a 3/8" socket wrench extender. Then found a 12mm socket that happens to fit the other end of the socket wrench extender and finally a socket to drill adapter to complete the driveshaft. You could get by with just a 1/4" socket wrench extender and attach it directly to your drill, but I did not have one.
You'll need a cordless or corded drill or whatever motor you can find that will spin the basket at about 1 revolution per second. Roasting coffee takes about 20 minutes so you will want some sort of clamp that you can attach to the drill to pull and hold the trigger. In my case I also need a couple of blocks of wood to support the drill at the proper height of the barbecue rotisserie brackets.
Next you need to prepare your barbecue grill. I think a gas grill is going to be the best bet here as I don't think you'll want a lot of smoke flavor in your coffee. You'll also need one that is setup with a rotisserie function or at least has the brackets for one. The motor that is used for rotisserie chickens is much to slow for roasting the coffee so don't bother trying to use it. Our grill came with some extra brackets that I use in the center of the grill to hold the roasting basket. I just shove them in between the two halves of the grill and hold it down with the weight of one of the grill grates. (see photo above) If you need extra brackets, you can make them or buy something like this.. http://www.charbroil.com/rotisserie-bracket-handle-side.html You'll also need to remove the grills under the burner that you're using to allow the roasting basket to fit.
Once you've assembled all your parts, you will want to clean up your grill as much as possible. I'm guessing chicken flavored coffee isn't going to be the next best thing :) Our grill has a "Clean" setting which runs the burners as hot as it goes and cooks everything to dust. I clean it up and run it on high until there is no more smoke coming out of the grill.
As always, please be careful and read all the safety requirements for the operation of your particular gas grill. The coffee you are going to roast is also going to finish some ware around 400 degrees or higher so please wear proper clothing, oven mitts etc. Also be aware if you forget about your coffee and cook it to oblivion, it could actually catch fire so please keep a close eye on things.
Step 2: Roasting Coffee
With the grill all cleaned and fired up you are ready to start roasting! I leave the grill on it's highest setting when roasting coffee and get it nice and hot before starting. I tend to roast a pound of coffee at a time but you can do less if you like. In order for your coffee to stay fresh and taste the best possible, you'll want to roast about as much as you plan to drink in a week or two.
There is a lot of good info on the internet for roasting techniques as far as ramping temperatures and creating repeatable roasts and the such if you're interested. I'll tell you how I've been doing it but feel free to adjust.
Pour your green coffee beans into the roasting basket and close it up. Next attach the assembled driveshaft to your drill and place the other end of the driveshaft on the square shaft of the roasting basket. It will be very hot inside the grill by now so use an oven mit to place the whole assembly on the grill. Set the slotted round shaft end of the roasting basket down on your centrally placed rotisserie brackets. As quickly as possible, start running the drill/basket assembly to keep the beens moving while they are being roasted. I run the drill at about 1 or 2 revolutions per second so place your clamp on the trigger to hold it in place. I leave the lid of the grill up for the first minute or two to make sure everything is working smoothly and to bring the beans up to temp at a slower pace in the beginning. If there are some small or broken beens in the basket they may work themselves out during this phase and end up on the burner. I like to carefully remove the fallen beans as they'll start to burn and smoke which may add some extra smoke flavor to the coffee. After the initial warmup I close the lid of the grill, wait about 4 minutes and then open the grill, check for any loose beens and close it back up. I do this about every 4 minutes throughout the roasting. As the beans roast, they will expel it's outer skin, which is called, chaff. It's kind of like a very thin paper that floats around in there and ends up burning up in the grill. By opening the lid every 4 minutes or so, you release some of the chaff and smoke associated with it and have found that it helps eliminate any smoky flavor in the final coffee. There is no real set time limit at which you will know when they are done roasting as different beans tend to roast differently. However, there are some things that you can listen for that will tell you when to stop. As you are roasting the beens, you will start to hear them pop like popcorn. It's a fairly loud sharp cracking sound and coffee roasters call this "first crack". This will be the first indication that you are getting close to being done. Once the first crack is finished, you could pull it off the grill and call it done but it's a pretty light roast. I tend to like a darker roast so I keep it going until the next indicator, "second crack" is underway. The first crack will stop and there will be a lull in the action for a minute or two, but start to get ready as things happen pretty quickly. When second crack starts, it will be a more faint cracking sound but can be more rapid. It has been described it as listening to rice crispies cereal. When the second crack starts, I start counting and take it off the grill about 30-45 seconds after second crack started. This results in kind of a light french roast. Here is some good info on the different roasts to see where you might want to take yours.. https://www.sweetmarias.com/library/content/using-sight-determine-degree-roast
Once you have your coffee roasted to the level that you like, you will want to cool the beans down pretty quickly to stop the roasting process. I take the roasting basket out of the grill and shake it for a bit to cool them down and to also release any chaff that might still be sticking to the beans. Next pour the beans out on a cookie sheet to finish cooling them down. Please be careful as the beans are very hot!
Once they cool down you will want to place them in a bag or container that will allow air to vent out but not let air in. The beans will vent CO2 so it needs to be able to escape the container but on the other hand O2 will start to make the beans stale. It's hard, but you'll want to wait about 24 hours or more depending on the type of coffee you roast before drinking your coffee. This allows the coffee to vent off some CO2 and it will taste better if you wait. It's interesting to try it daily as it does change a bit over time.
After all that, grind it up and enjoy!!