Roasters log 1

So I’m up to roast number 7 at this point (probably 8 or 9 by the time I’ve finished this blog post…). I’m beginning to think maybe I like the process of roasting coffee more than drinking it - my biggest issue at this point is that I can’t iterate quickly enough on the roasts because I don’t drink coffee quickly enough. I only want to roast enough coffee for about a 5 days worth of drinking, i.e. ~5 batches in my wee popcorn machine, since apparently the “freshness” really starts to fall off after 5 or so days. I’m tempted to try and foist it on my friends, but I think I need to try and dial it in a bit first.

Yesterday I picked up a copy of Home Coffee Roasting: Romance and Revival from the library. I’ve been jumping all over the book, but so far it’s been great. I’ve already locked in my roaster, so a lot of advice about what the options are is somewhat wasted on me, but probably the most important thing in there is keeping a log.

Which I wish I’d been doing from my first roast, but I was a bit excited to get started. As a result my first couple of roasts were all over the place in terms of quantity, darkness etc. I was messing around, rather than experimenting. Exhibit A being this “innovation”:

potted coffee roaster

While it definitely sped up my roasts I don’t think it added much to the flavour. The thing I have stuck with, however, is using my wife’s hairdryer on a ‘cool’ setting to cool the beans after I dump them out of the roaster. This is to try and stop the roasting process as fast as possible once the beans have left the roaster. Due to the residual heat inside the beans it would otherwise continue for a while after they’re dumped out of the roaster. It also helps get rid of bits of chaff still stuck to the beans.

Anyway, what I’ve noticed so far is there’s a pretty reasonable amount of variability. Between my sixth and seventh roasts the first crack (when the coffee beans make a cracking sound as they start to undergo pyrolysis) happened at 2 minutes, 15 seconds and 3 minutes, 7 seconds respectively. That’s 52 seconds, or about a fifth of the total time I spent roasting the beans (I targeted 5 & 6 minutes for those roasts). As you can see from the picture below, there’s only a slight difference in colour as a result. roasts 6 and 7

I’m not sure what’s causing that variability. I don’t have any effective means of measuring temperature, yet. I tried some digital thermometers that are rated up to 300°C, but although the probe might have been fine at that temperature, the display most definitely was not. I’m planning on drilling a hole through the side of the tin can I’ve put over the top of the metal “cup” and pushing the probe in through there to stop the display from overheating. Need to pinch a drill from my dad’s place first though.

I’ve also ordered a thermocouple from China by way of eBay, but of course that’ll probably take a month or so to show up, but when it does the amount of science I’m gonna be able to do is gonna go through the roof (I’m talking like continuous profiling and pretty graphs and stuff). Really looking forward to that.

So that means only variable I can effectively vary at this point is roasting time. (I need to get a scale as well) So I’m gonna totally try and science the hell out of that in the meantime. Based on discussions online it seems like I should be trying to target longer rather than shorter roasting times at lower (average) temperatures. Unfortunately I don’t have any way of controlling that, and I’m in a country where 240v is the standard, so the machine I’m using is a 2400 watt one. This probably means it’s heating up way to fast (I was seeing 200°C on the thermometer within a couple of minutes before the display gave out on me.)

The other thing I’m somewhat intentionally sacrificing control over is the amount of time the coffee is resting for between roasting and drinking. At the moment I’m laying in stocks until the weekend, when I should be able to get a scale to further refine the process. At that point I’m gonna try and consistently roast every day so we’re always drinking the coffee the same number of days after the roast.

Lots of variables to keep track of. At least the coffee I’ve produced so far is drinkable, and it’s definitely cheaper than buying it from the supermarket. The ideas that are bubbling out of my head in terms of potential improvements are numerous enough to keep me busy for a while, let alone the process of refining what I’m already working with. So I’ve hit at least a couple of my goals, and so far I’m definitely enjoying geeking out on the process.