Heat Gun / Soup Can Nano-Roaster

I'd been roasting with a HG/DB heat gun and dog bowl for several months. I liked the simplicity of a heat gun, a steel bowl, and a wooden spoon. Roasting sequential batches was tiring, though, so when I happened upon Tim Eggars soup can roaster — which I stumbled upon through homeroasters.org — I had to try it. (If you're ever hunting for ideas, or for proof that this hobby can turn into an obsession, you also might want to check out Sweet Maria's gallery of do-it-yourself roasters.)

Tim uses a gas burner underneath the can, but I, as others have done videos showing various strategies have disappeared from photobucket, aim the heat gun into the can. This creates an asymmetrical heat source. To adjust for this, I tilt the can. And I angle the agitating fins to move the beans toward the center of the can. The diagram at right tries to shows the placement of the fins.

I originally used pop rivets to secure the fins, but Eggars' method of cutting slots with a Dremel is quicker and easier, and beans are less likely to get stuck. With a pop rivet, the entire fin is inside the can, and beans can become caught where the fin bends.

This setup is good for test batches, roasting 2 to 3 oz at a time — or around 8 - 12 brewed cups of coffee. (For 3 oz batches, I angle the can higher, and tip the heat gun downward a bit.

Here's the can itself. I'd planned to wrap it in fiberglass insulation for roasting outdoors. But the rag I used as a stop-gap measure works well enough. I'm roasting indoors, now, and the rag allows me to keep the heat gun on a lower setting. And it helps prevent burns — though the hose clamp still gets plenty toasty.

After several months of use, small cracks began to radiate from the hole around the bolt, due to the constant thermal pounding. So I replaced the original bolt with a sturdier one, and placed washers on either side of the can to shore it up.

The soup can is actually a stew can — the same diameter as a wide-mouth canning jar ring.

The foil that partly blocks the can's opening I cut from a Stouffers macaroni and cheese container. 3 or 4 tabs protrude from the outer edge of the foil and are under the canning ring to keep the foil in place. The wider section of foil blocks the beans as they tumble over the front fin.

In this interior shot, the front fin is on the left. If you compare the angle of the fin to the concentric rings on the sides of the can, you can see that the fin is not perpendicular, but runs at a slant.

The can rotates counter-clockwise, so when the beans tumble over the front fin, they should also slide back toward the middle of the can.

Tim Eggars' design has the advantage of a good, uniform heat source along the bottom of the can, but I'm fond of the heat gun because I don't have to deal with combustion gases, and I suspect it uses a little less energy overall. By angling the fins, the beans roast fairly evenly, and the heat gun roast retains more of the aromatic flavors typical of an air roast. (That's my pet theory, anyway.)

Here's the setup, ready to roast. (If you happen to have a heat gun and cordless drill already, materials cost $5.00 - $10.00.)

You can barely make out the smaller hose clamp at the bottom of the drill's handle, just above its battery. Once you've adjusted the clamp to produce 40 - 50 rpm, you can slip it on and off the trigger without further adjustments. You want to keep the beans moving, but not so fast that they bunch down toward the bottom of the can.

The heat gun is positioned so that it doesn't blow directly on the beans. Due to the angle of the can, the blast of hot air primarily hits the back of the can above the beans, although they are lofted briefly into the heat by the fins. I'm trying to avoid cauterizing the surface of the beans with a direct blast of air.

The drill is propped up to help prevent beans from spilling. The drill and its prop are sitting on a thin piece of plywood, which makes it easy to slide the can nearer and farther from the heat gun. Distance is how I manipulate heat.

My $20 heat gun has a low (700f) and high (1000f) setting. When roasting outdoors, low was too slow, particularly in cooler or windy weather, but since moving the setup indoors, I've been roasting entirely on low. (Notes about roast "profiles" are here.)

Below the can is the cooling tray — just a cardboard box with the bottom cut out and a piece of hardware cloth duct taped inside. Eventually I'll build a light-weight hemlock box.

The entire contraption sits below an ancient ceiling fan in our out-of-code basement bathroom. When the roast is finished, I dump the beans into the box, then hold it under the fan.

The beans cool in about 1 minute. At right is 2 oz of Guatamala Oriente cooled just as it entered 2nd crack.

Here's a short, uneventful movie of the roaster in action. The beans are a couple of minutes prior to 1st crack. In this otherwise unremarkable video, you can see the chaff is separating from the beans and blowing out of the can. In another minute or so, I'll move the nozzle into the can for the final approach to 1st crack.

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Other roasting methods I've tried

Below is a 24-second double shot from 15 grams of Brazil Ipanema Tree Dry Process beans. (They're from a 4oz batch roasted in the Behmor. The Behmor was set for a 1/2lb on the P2 C profile, and the roast was cooled 6 snips into 2nd crack).

Producing something like this.


The crema on this 1.5oz double shot is thick and fairly uniform in color. A 0.75oz ristretto will be darker and less uniform. (The pictures of a few pours mainly show patterns in divided double shots or ristretti.