Roasting Coffee with a Heat Gun

I recently became disappointed with generic department store whole bean coffee. I had heard rumors that cheap green coffee beans were available on the internet. I decided to try roasting my own coffee. Here is the story so far.

Hot air popcorn poppers are reported to be a good starting point for home roasting but after looking in the garage, checking a few yard sales and thrift stores, I gave up and decided to try a heat gun. I have two heat guns. The other requirements: a big metal spoon, a stainless steel bowl and a metal cullender.

My first green beans came from Smokin' Beans. Five pounds of Peruvian Villa Rica in a burlap bag.

October 16, 2016. Roasting in a steel bowl, constantly stirring with metal spoon and also stirring with the nose of the heat gun, an old 1200 watt Craftsman gun. I tried stirring with a wire wisk at first but it was too short, got too hot to hold. I heard the first crack around 10 minutes, roasted till what I thought was the end of first crack. Not sure. Green roaster, me. It was a 15 minute roast.

After the roast, I poured the smoking beans into the cullender, stirred them around, poured them back and forth between bowl and cullender to cool them. My first jar of roasted beans:

I'm not going to describe the coffee using the words I have found in my coffee research. What does "bright acidity" mean? What could it possibly mean??

I was too anxious to try the coffee and ignored the ubiquitous advice to wait 24 to 48 hours before brewing. So my first cup, brewed the following morning (about 12 hours after roasting) had some odd flavor to it. The following day it was better and the next day it was better still. I am not a coffee connoiseur, but I can say without doubt that the fresh roasted coffee is much better than the bitter, stale department store coffee. No surprise, right? Right.

So I continued to experiment. Roasting in a bowl has its pros and cons. I love watching the beans change color. The random stirring of the beans results in a variety of colors in the bowl like autumn leaves. I get a close up nose full of the roasting aromas that constantly change during the roasting. The bowl method is labor intensive, however, and it could be hard to get an even, consistent roast.

October 22. More research resulted in a flour-sifter roaster. A power drill spins the vanes in the sifter keeping the beans in motion to prevent scorching.

The heat gun shoots heat up through the bottom of the sifter. Efficient transfer of heat to the beans.

This works but it has two major drawbacks. The screen on top (necessary to keep the beans from flying out...) prevents a good view of the beans. A view of the bean color helps determine the end of the roast. The roaster is too noisy to hear the beans cracking!

November 10. I decided to automate the steel bowl method. After various prototypes, I have the working model pictured below. The roaster as pictured cost me nothing. It's made of junk I had lying around. On the top left is an old computer power supply. I'm using a 5 volt, 25 amp wire from the power supply to turn an old 12 volt windshield wiper motor bolted to an old leaky stainless steel sauce pot. There are stainless vanes screwed into the sides of the pot to keep the beans tumbling as the pot turns.

Here is another view showing an $8 heat gun I got on sale from Harbor Freight so the roaster can have a dedicated heat gun. This view also shows a wooden lid I can swing down to keep the heat in the pot.

This roasts 12 oz. of green beans to medium-dark in about 8 minutes. Every roast is an experiment as I try to define the end of the roast. I can watch the bean color change, I can smell the beans roasting and I can hear every crack and pop. I use an infrared thermometer to get an approximate bean temperature. At the end of the roast, I dump the smoking beans onto a window screen in a wooden frame...

...and sit it on top of a box fan to quickly cool the beans:

See the roaster working in this video:


November 2016

January 2021 update. The coffee roaster still runs great, 2 or 3 times a week. The high-temperature element of the heat gun burned out about a year ago so I replaced the heat gun with another one from Harbor Freight. I covered the air intake holes with aluminum screen to keep chaff out of the gun. The heat gun wobbled a little in the old mount, so I modified the heat gun mount to hold the gun more securely. The picture below shows the modifications.

I am still using the same wooden lid. Yes, it's a little charred but the roaster works as well as ever, evenly roasting beans from anywhere in the world.