Home-roasting coffee beans

There comes a time in a coffee geek’s journey when one considers the possibility of roasting coffee beans at home.

This appeals to me. It feels like a return to the raw origins of coffee where artisanal dedication combines with ritual honouring – much like I believe tea ceremonies of the Geisha to be.

I was always somewhat deterred from home roasting, understanding it to be a very precise and technical process (which it can be) requiring modifications to heat guns, popcorn machines with lots of margin for getting things horribly wrong (which can happen).

I’ve spent a bit of time poking my nose around roasteries, talking to professional and passionate roasters. So after being offered a large handful (or two) of green beans to experiment with, and with a firm belief that there must be a relatively simple way to roast at home, I came up with the following:

A pot, with a lid, over a gas flame.

My first experiment was with a pan because I believe this is the traditional method. I prefer a pot primarily because pots have sides and lids which aid in two factors.

Even roasting

You can’t just throw beans onto heat and wait for them to pop. One spot on one side will get burnt while the rest of the bean may not be roasted enough. The beans need to be turned so that, as best as possible, there is equal distribution of heat over the entire surface of each bean. This is why the professionals use roasting drums that rotate.

Trying to turn beans in a pan is (in my limited experience) impractical and inefficient – not to mention the challenge of keeping the beans in the pan.

Beans in a pot allow you to lift the pot over the flame and then agitate the beans by swirling them around so they bounce off the walls, turning randomly over (much like they would in a rotating drum) and remaining in the pot with the help of the lid.

Here’s the catch: it’s a bit of work. But you only need to keep this up for 10 – 15 minutes (or thereabouts) and only in spurts. I tend to let the beans rest for 30 seconds and then I agitate them for 30 seconds.

Heat distribution

In a pan the only heat source is the bottom of the pan. With a pot the walls also give off heat, and with a lid the temperature of the air around the beans is raised. While I can’t say for sure, I’m pretty sure these two help speed up the overall ‘roasting’ process and contribute to a more even roast.

Method

Like brewing coffee using a moka pot, I feel this will be a very personal process and something each person will develop to their own preference with experimentation. So for here I keep it simple:

1. Heat the pot with lid on as hot as you can get it without creating any danger
2. Get the quantity of beans to be roasted ready – not more than what will fill a quarter to a third of the pot you are using so that there’s enough room for them to move around to achieve an even and consistent roast across all beans.
3. Drop the beans into the pot, replacing the lid, and agitating the beans frequently, keeping a mental note of:
   1. the sounds you hear, such as the sound the beans make when being agitated (it does change during the roasting process), and listening for popping sounds
   2. the smells as they change
   3. the colour, size and ‘texture’ of the beans as they become more roasted
   4. the feel of the beans as they are agitated, which should correlate with the sound they make
4. At some stage during the roasting process you’ll want to drop the heat to slow the roasting process. Essentially the heat from the outer edges of each bean becomes the source of heat for roasting the inner parts of the bean. You want sufficient heat to maintain that process but not so much that the outer bean becomes over roasted (or the outer bean is perfect but the inner part is under roasted and still hard).
5. When your feel the beans are sufficiently roasted, according to your preference and experience, take them off the heat and head straight outside with one or two metal colanders and/or sieves. Pour the beans into the colander or sieve and begin agitating again to cool the beans down as quickly as possible, halting the roasting process (yes, some more effort but much easier). I like to use two, pouring the beans from one to the other. Blowing gently on the beans while doing this, if there isn’t a light breeze to assist you, will clear the beans of the chaff that forms during roasting.

Tips, Tricks and Considerations

I imagine heavy-based or cast iron pots that hold and distribute heat would probably be better, but do factor in that extra weight with make agitation more challenging.

I’ve seen (pictures of) manual popcorn pots that have agitators build in but unless they reliably turn the beans (rather than simply sliding them over the surface) I’m hesitant to suggest them as an alternative.

Glass lids give you a view, clearly… useful for getting an idea of the colour of the beans as one indicator of when you should stop the roasting process.

Lids also keep the smoke contained as roasting coffee beans can be a rather smokey experience once the moisture starts being released from the beans.

That however presents a concern for me. I don’t feel it’s good to have too much moisture build up inside the pot as I believe this could have a negative effect on the quality of the roasted beans. My suggestion is to release the steam by opening the lid briefly every other minute or so once that part of the roasting process in underway. If you’re using a glass lid this will be obvious.

And one final thought: I wonder if the ‘inaccuracy’ of this method doesn’t add a nuanced complexity to the brew that is otherwise created by blending beans? We know that the lightness to darkness spectrum of roasting brings out different characteristics of the bean so perhaps a somewhat uneven roast with a mix of less to more roasted beans is a Not So Bad thing. This is artisanal after all.