Heat Gun Dog Bowl Coffee Roasting

Christopher Swingley

Introduction

Roasting coffee is really easy. All you need is a heat gun, stick, dog bowl, colander, and a pair of leather gloves. Oh yeah, and green coffee. You also need a heat resistant surface on which to roast. I'm using a fairly expensive Milwaukee heat gun, but less expensive Wagner and other models work well too. You want one that's 1200 watts or greater, and that doesn't blow a lot of air like a hair dryer. With my Milwaukee you can feel the hot air coming out, but a foot away from the nozzle all you'd feel is heat, not blowing air.

I'm using a soft maple offcut for my stick, but pretty much anything would work as long as it won't melt and doesn't have any resins, oils or other finishes on it that could melt with the heat and affect the flavor of the beans.

I'm using a regular 2 quart dog bowl, but I've also roasted in a heavy colander, so really anything that holds the beans and most of the heat should work. A 2 quart dog bowl is just about right for roasting 10 ounces of beans. I've never tried roasting more in a larger bowl, but I would guess that as the bowl size and bean volume increases, you would no longer be heating the beans evenly enough. For your dog's sake, don't use his or her bowl. You can see in the photos that the bowl accumulates coffee oils and I doubt if it's good for your pet.

The colander and gloves are used at the end. I pour the beans back and forth between the hot (!) dog bowl and the colander, which cools them, and allows some of the chaff to blow away. Picking up a hot dog bowl with your bare hands is a bad idea, and it's also a mistake to use your normal colander for this, since over time it will accumulate coffee oils.

In the winter I roast coffee on the concrete floor in our garage, and in the summer I use several fire bricks to keep the heat from burning the wooden box I roast on. Any sort of tile, bricks or other reasonably well-insulating material would work.

We get all our green coffee from Sweet Maria's. They've got a great web site filled with useful information, they travel all over the world in search of good coffee, and they sell a lot of coffee from small, local farms, often with Fair Trade and Organic branding. It's obvious from their site that they're really invested in bringing good coffee to their customers. If you can find green coffee sold locally, that's probably better, but if you're shopping on the Internet, I highly recommend Sweet Maria's.

The image on the right shows the setup before I've started roasting the beans.

Roasting

The images on the right show the roast as it proceeds. Click on an image to see a larger version.

The idea is to evenly apply heat the beans by moving the heat gun over the beans, and at the same time, stirring them with the stick. I like to move the heat gun in one direction and stir the beans in the other, but the exact mechanisms aren't really all that important. Once the beans get hot enough, a self-sustaining endothermic reaction starts and the beans will be heating themselves and each other.

Different beans will roast in different ways, and some are more tolerant that others of the heat from the gun. Generally speaking, the denser, smaller beans can handle more heat applied to them than the larger, lighter ones. When I first roast beans I've never roasted before I try to keep the end of the heat gun about even with the lip of the bowl when I'm roasting, moving it over the surface in that plane. If the beans don't seem to be roasting quickly enough, I will lower the gun somewhat into the bowl. You can tell if you're roasting too quickly if the beans are darkening too quickly and don't seem to be going through the normal stages shown in the images and discussed below.

Keep in mind that every roast is a little different, and between the outside temperature, beans, and the heat gun you're using, the timing of the roast won't necessarily be the same every time (or the same as the times I've got listed here). Unless your roasting is taking longer than twenty minutes, or proceeds from green to dark and oily in less than five minutes, everything is probably OK.

Every roast should go through a series of stages. The beans start out hard, dense and green. After a few minutes of roasting, they'll start getting lighter green, and eventually turn to a yellow or tan color. At this point they lose the sort of waxy smell they have to start, and begin to emit a more coffee-like, roasted odor. Some beans will also start throwing off their skins and chaff my start flying around in and outside of the bowl. Sometimes the heat from the heat gun will ignite the chaff, but I've never had a problem with this. Normally the beans are tan between four and six minutes into the roast.

As the roast proceeds, the beans start to get darker and darker and the smoke starts to smell more and more like roasting coffee. Initially, some beans will be getting brown, while others remain light green or tan. Don't worry about it. Once the beans reach a certain point, they start heating each other. Just make sure you're not leaving the gun in one location too long, and that there aren't cool spots in the bowl because you're not mixing them enough. I usually pass the stick through the middle of the bowl every few turns around the bowl so beans don't get stuck in the middle where it might not be as warm.

The beans will darken from tan, to brown, to dark brown, and eventually they'll get very dark and start to get shiny and oily looking. Learning to recognize the colors, sounds, and the smells of the beans as they roast is the most important part of getting perfectly roasted coffee, just the way you like it. Heat gun dog bowl roasting has a great advantage over other roasting methods because the entire process is in the open where you can use all your senses to judge the roast.

At some point in between brown and dark brown, but generally before the beans start to look oily and really start to smoke is "first crack." You will know it when you hear it because the beans will actually audible, making loud, sharp popping noises a lot like popcorn popping. At this point the beans have reached the level of "City Roast." The amount of time you continue to roast the beans beyond City, determines what the coffee with taste like. In general, beans that are cooled before reaching first crack will taste sour when brewed, so the first time I roast a new bean, I always take the roast at least to when first crack is winding down before cooling the beans.

In the images on the right, first crack started right around seven minutes, and continued through eight minutes. I don't like very dark roasted coffee (like Starbucks, for example), so I stopped the roast after first crack was finished (after about eight and a half minutes).

First crack will continue for a minute or two as individual beans get up to the internal temperature required. At this point, the roast is self-sustaining because of the reaction triggered inside each bean. You can draw out the length of time between first crack and the next audible stage (logically called "second crack") by moving the heat gun farther away from the beans. As long as you give them a little heat, they'll keep roasting.

As mentioned, if you keep roasting after first crack has stopped, you will reach second crack. The beans will make another cracking sound, but it's quieter, more subtle, and tends to be more condensed than first crack. In first crack you can hear the individual beans popping, but in second crack, it's more like a general crackling sound as multiple beans reach that stage at the same time. The beans will normally be very dark brown and start to look shiny from the oils reaching the surface.

At second crack, the beans are at what's called "Full City Roast". There's generally less "origin character", but more roasted flavors than beans that are stopped at a City Roast. If you buy your beans from Sweet Maria's, the bags have suggestions about where the bean should be roasted to get the most out it.

The roasting reaction is going full bore between first and second crack, and the beans will really start to smoke heavily. And as you get closer to second crack and beyond, the smokiness will smell less like roasting coffee and more like something is burning. I can usually tell just by the smell when it's appropriate to stop roasting because I don't like the flavor of well roasted beans.

If you continue beyond second crack, the beans will get darker and more oily. When they're basically black and covered with a shine, you've reached Vienna Roast, and if you continue, you'll get to French and then Spanish Roast. By Spanish Roast, the beans are basically burned on the outside and most of the flavor and body compounds in the coffee will have disintegrated. Unless you prefer really dark roasted coffee, you probably don't want to go much past a Vienna Roast. Espresso roasts are usually taken to Vienna or French Roast, so well beyond second crack.

Cooling

Once you're satisfied with the level of the roast, you need to stop the reaction that's going on inside the beans or the coffee will continue to roast itself even without adding more heat. Some people lightly spray the hot beans with water, but I like to pour the beans from the dog bowl to a colander and back again to cool the beans. I also blow on the beans as they're passing between the two containers to remove some of the chaff. As far as I've been able to tell, the chaff doesn't affect the flavor of the beans or get in the way of my grinding, so I don't worry too much about it. After a few passes through the air, the beans are cool enough that the reaction has stopped. It'll still take an hour or so for them to cool off enough for you to put them in a jar.

After they've cooled, put them into a jar and they'll be ready for brewing. Freshly roasted beans keep changing, and some beans taste best eight to twelve hours after roasting, while some peak as much as three days after roasting.

That's really all there is to it. Enjoy!

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[ Page last updated 15-Apr-2007 ]