Enjoy delicious coffee with beans that you've roasted all by yourself. All you need is the right kind of cheap popcorn popper and some raw beans. It's really easy and so totally worth it.
If you grind your own beans at home and look forward to that first hit of caffeine in the morning, then this is for you. With just a bit of effort you'll be enjoying it so much more.
Warning: doing this and getting good at it has the potential to turn you into a coffee snob who complains that coffee shops are burning their beans. Just keep it to yourself because few other people will care, OK?
Step 1: What You Need - the Basics
The core element here is the air popcorn popper. Mine is the Toastess TCP-713, but there are many others that work as well. The key is to get one that has its air vents on the side of the main chamber and a solid bottom. There's more info about that here and here.
If you're willing to trek through some thrift stores you might be able to find one of these for $5 or so. Otherwise, it's not too bad to get a new one for under $30.
I got the raw beans from Sweet Maria's in Oakland. They offer lots of different beans for $6-$8 a pound. I'd recommend getting the sampler which can get you 8 pounds for $40 or $5 each.
The last part you'll need is a couple of metal bowls or, even better, colanders.These will be used to catch the chaff and cool off the beans.
Step 2: What You Need - a Little Fancier
If you want to have more of an insight into the process you can install a thermometer into the lid. Drill a hole into the top, insert a flattened tee nut, and insert the thermometer.
For the thermometer you'll want one that can go up to at least 450, but 500 would be even better.
Step 3: Let's Go!
Enough chitchat, let's roast some coffee!
Fill the popper up to the max fill line with the raw beans and turn it on. That's it your beans are now heating up and moving in circles.
After a couple minutes small pieces of chaff will be coming off of the beans. If this doesn't bother you (maybe you have a sawdust floor?), then just watch it fly. Or you can be like most people and catch it with one of your bowls.
After that you'll hear a cracking sound, almost like popcorn popping. After this has happened you now have roasted coffee. How much longer you leave it in for determines just how roasted it gets. Here's the scale of roasts:
Full City (444F)
Full City + (454F - second crack happening)
French Roast (474F)
Fully carbonized (486F)
Imminent fire (497F)
After doing this for a while I've been happiest with the City+ level of roasting. The flavors stand out and you can really tell the differences between beans. You can also see that the popular French Roast is essentially the last stop before death. A lot of the flavors are gone and it's very bitter.
Back to the roasting! When you're ready to pull the beans, turn off the popper, carefully take off the plastic lid (it's hot!) and pour the beans into the bowl or colander. Now shake the beans around and around to cool them off as quickly as you can as they're still roasting.
Step 4: Enjoy
Now you have roasted coffee. Don't get too excited and grind right now, though. The beans will offgas CO2 for a little while. Let them sit in a lightly closed container for 12 hours and then seal in an airtight container. I like using old jam jars.
Grind the beans after 24 hours or so. They're good for about 5 days. Since you can always roast just a little more this is a great way to enjoy fresh coffee even if you buy several pounds of raw coffee at a time. Raw coffee is good for 6-12 months.
A big, big thanks to Sweet Maria's for almost all the information in here as well as being an excellent source of beans.