Roasting with Frankenstein
When you decide to roast your own coffee, you really have two options for the equipment. On the one hand, you can buy a $500 roaster. You'll have to purchase a new one every 2-3 years if you do this, for the dubious convenience of having a prefabricated commercialized roaster. On the other hand, you can build your own roaster. Going this route offers complete control over the costs involved, from an unmodified popcorn popper (about $15 at Target) - which can roast about 1/8 pound at a time - to a fully custom roaster. Custom roasters can involve almost anything, including high-dollar thermocouples, variacs, and even more arcane electrical-engineer-geekish equipment. Either way, you're going to have to learn how to control your roast by watching temperature, paying attention to what your ears and nose tell you, and stalling the roast at appropriate times in order to hit different roast profiles.
In my case, I chose to take a middle-ground approach to building my own roaster. Regardless of how much I like my coffee, I would have a hard time justifying $150-250 per year just to have the ability to roast. When I started roasting, that $15 popcorn popper looked pretty attractive, particularly since I didn't know whether I would completely suck at roasting. The unmodified popper gives you just enough coffee to make you wish you had more time to roast, and the resulting roast is about as repeatable as cold fusion. Needless to say, I desired more for my roasting experience. After reaching this point in my roasting education, people began to ask on a regular basis whether I had burned anything down yet.
The first problem with the roaster is the fire-safety features. If you follow this path to roasting nirvana, you'll know what I mean the first time you do two back-to-back roasts, about halfway through the second roast. It's hard to miss: the popper simply stops, dooming you to a batch of half-baked beans. The trouble here is a pesky heat-sensitive safety switch deep within the popper. As time goes on, it gets harder and harder to disable this switch. It's not because the switch itself is harder to disable; it's because the manufacturer is making it harder and harder to get inside the case of the popper! It's outrageous - it's almost like they don't want you to disable the damned thing! Oooo-oooo, save me! I'm going to burn down my house! (I've found that most people actually agree with this outlandish conservatism...hence the questions.)
:-)
Anyway, I did eventually get into the popper - I'll refer to it as a roaster from here, since it's not a popper anymore - and did route around "safety" switch. This allowed me to roast more than one batch at a sitting, which is great. However, I still had almost no control over the roast profile. As an aside, the profile is the plot of temperature change over time. It's not just about getting to a particular temperature; it's more like reaching certain temperature milestones in a particular set of times...but I digress. I needed more control.
I had to do a lot of googling to find this, but eventually I learned that the motor powering my roaster fan was getting about 12VDC when it was rated for around 20VDC. Also, I decided to separate the heating circuit - which is AC - from the DC fan motor. This would allow me to turn the heat off without shutting down the fan, and control exactly how fast my beans heated up. I rummaged around the house for a suitable power supply, and eventually wound up with an old laptop power supply which ran at 19VDC. After wiring this to the fan motor in place of the diode bridge (which was another weak point...they blow out much earlier than the fan itself), and running both circuits to a custom-made control panel made of homewire, light switches, and home power outlets, I have complete control over my roast. Also, with 19VDC of power running to the fan, I can roast 1/4 pound of greens at a time! Two roasts, and I'm done for about ten days. Oh, and I added a candy thermometer so I can monitor temperature, and a wire-mesh colander to catch the overflowing beans in the roaster.
All told, I spent $15 on the popper, about $7 on parts for the control panel, and $8 or so for the candy thermometer and colander. Sure, I was lucky to find that power supply, but even if I'd had to find a different solution. Sure, my roaster won't win any beauty pageants. Sure, my neighbors and family look at me like I was dropped on my head as a small child. But you can't argue with good coffee. And with a $30 dollar roaster capable of six months** of roasting, I can afford to buy a lot more of this.
** In the interest of full disclosure, I should mention that the popper fan doesn't last forever. The beans put quite a bit of strain on it, and eventually the motor just melts down. I'm still an electronics-geek-in-training, so I'm not sure what the technical term is, but when it happens, the motor is dead beyond revival. I've gone through about four popper motors now, and each time it gets harder to retrieve the motor...the last one required cutting it out of the housing with my Dremel. I've added a fuse to the system, running at 3 amps, to see if I can prolong the motor's life. But even figuring $15 every six months, this is a cheap roaster!
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