- Preheat the oven to 430F (220C). I use an oven steel and let it preheat for an extra 10 minutes.
- Evenly spread green coffee beans on a paella pan or baking sheet lined with parchment
- Put the paella pan or the baking sheet in the oven, turn the vent hood on
- After 25 minutes, take the coffee from the oven, let it cool
- Optional: Clean away the chaff - I put it in the colander, rub the beans, and as I toss them I gently blow the chaff away.
- Preferably let the coffee air for about two days before using.
One sunny morning Jasna and I found ourselves eating breakfast at Coffee Shack in Captain Cook area of Hawaii. We were told that Coffee Shack was known for its excellent breakfast and for a spectacular view, and I can confirm that both were true, we went back several times. A waiter comes and asks us whether we would like some coffee. I acted as my usual self, put my nose up, and declared I did not drink coffee, and asked for tea. Jasna tends to be smarter than me, so she asked whether the name Coffee Shack meant that they had good coffee. She did the homework and knew about Kona coffee. I just tagged along.
The waiter smiled and pointed to the steep slope just under the restaurant: "Yes, we have good coffee. It comes from our plantation right here!" Jasna ordered coffee, she barely prevented me from drinking all of it, and that was it. The flavor was strong, yet smooth and not bitter, very pleasantly complex. Quite a difference from the awful bitterness people drank back in Slovenia. We became coffee drinkers, and by the time we returned home, Amazon already delivered a coffee-making apparatus.
It turned out that friendly folks at Coffee Shack are very happy to sell you their coffee beans, and that they even do mail order. We have been loyal customers - we consume very little coffee, so we decided to go with the very best. Recently, our friends Rok and Ying visited, told us about a freshly roasted coffee in a local Ethiopian restaurant called Walia, and how they learned one could buy green coffee beans from Selam Market in Campbell. For quite some time I have been tempted to try to roast coffee, but I never really crossed the threshold of looking for the beans. I went to Selam Market the next day and returned with a large bag of green beans. I expected a lengthy trial and error process, so I thought I better stocked up.
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| Green coffee beans spread on the baking sheet |
Here is what green coffee beans look like, this is about 5oz. I asked my friend Google to point to instructions for roasting coffee beans and I found quite a lot of pretty consistent information. Pretty much everyone recommends to get a popcorn maker and use that for roasting beans, and some even recommend using a heat gun! Many people describe in detail the transformation of coffee during the roasting process. It all looks very doable, but it does require practice and it all seems to be error prone, even if one purchases a dedicated coffee roaster.
I gave it a try and roasted coffee in my wok on the stove top. Those web sites were not joking, the transformation is really interesting. The coffee about doubles in size, it makes cracking sounds in two places in the process. The amount of smoke generated surprised both me and our fire alarm. Of course, I roasted at too high heat for too long and ended up burning the beans. Oh well. I discarded that batch promptly and tried again, this time being much more careful. This time the result was quite uneven, but the coffee that I brewed from those beans was very good.
The unevenness and the anticipated lack of consistency made me consider shopping for a popcorn maker, or even a dedicated coffee roaster. Remember, tools are good!!! Argh!!!! ... said Tim the tool man. Then something clicked. Everyone was recommending to roast at a very high temperature, yet some listed average internal coffee temperature for different stages or styles of roasting. So being a researcher and all I thought - all one really needs to do is to bring the internal temperature to what it should be, and my oven very happily heats up to the desired temperature.
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| Coffee after half and hour at 435F |
An experiment started. I set my oven to 435F convection, spread the beans on a baking sheet, and put the sheet in the oven. I did use parchment paper simply because I like to use parchment instead of cleaning the baking sheet. I decided I would roast the beans for about 20 minutes after the oven reached 435F, and in the subsequent experiments I converged to 26 minutes at 442F. I also remembered to turn on the ventilator in the range hood, which proved to be a good move. I was curious what would happen, because Sweet Marias, the Cadillac of sources for green coffee beans, claimed one needed a perforated baking sheet to allow movement of the air, and that roasting in the oven would produce uneven results. But they roasted at 500F for 15-20 minutes.
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| Coffee bean chaff, removed |
I was surprised with how evenly the coffee was roasted. In the picture you can see how much chaff is attached to coffee beans. So the next task was to remove the chaff. I happen to have two metal colanders, so I transferred the coffee in to one and after it has cooled down enough to handle with hand, I started to stir and rub the beans. And when I got bored with that, I would pour the beans from one colander to another. I read about that in one of the web sites. I suggest one does that over a sink, unless you enjoy your place to be super messy.
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| Cleaned coffee |
I found out that the chaff goes away quite easily, but not completely. Here is what the result looks like. See how some chaff is still in the cracks? I decided the chaff would be filtered away when I was making coffee, so not a second of sleep was lost due to my coffee not looking exactly as clean as the coffee from Coffee Shack.
With some more experimenting I decided that the coffee really does need to degas and that the peak flavor develops in about two days after roasting. Your personal preference will come in play here.
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| Our excellent retro-grinder |
Let me quickly describe how we make coffee: We use a hand-cranked ceramic burr grinder one can get for $35-$45 on Amazon. It takes about a minute to grind two scoops of coffee beans, which is Jasna's and mine combined daily consumption. An electric grinder of equivalent quality would be several hundred dollars, and it would consume tons of our non-existent counter space. So we went old-fashioned, much to a surprise of our guests, who, I am sure, find us a little quirky, yet tend to appreciate the quality of coffee, and the meditative aspect of the brewing process :-)
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| Ground coffee in the upper chamber |
For the brewing, we use a siphon where we replaced the original cloth filter with a glass rod Corey filter one can get on eBay. It is much easier to clean than the cloth filter, and people say that cloth traps some of the coffee oils. Speaking of clean-up, I clean the siphon in about one minute, and I am still puzzled with people complaining it is a lot of effort.
The way the siphon works is very neat. One places the ground coffee in the upper chamber of the siphon with the filter already in place. Then you set the upper chamber in the stand so that you can fill the water in the lower chamber.
I always fill the bottom chamber with boiling water because it takes quite some time for the water to heat up. I read that some people believe pre-boiling the water deprives it of oxygen, which results in inferior coffee. The scientist in me has a difficult time believing such a claim, the water boils one way or another.
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| Siphon with the water pushed up |
When the water is in the lower chamber one sets the top chamber on top of the bottom chamber, creating an air-tight seal. The whole contraption then goes on the stove burner at a medium heat. As the air in the bottom chamber heats up and expands, it pushes the liquid to the top chamber. At that point it is good to lower the heat a bit. Apparently the siphon keeps the water at exactly the right temperature for coffee brewing, a few degrees under boiling. Moreover, some of the air is pushed from the bottom chamber, and that air creates bubbles that mix the ground coffee with the liquid continuously.
We brew our coffee for 2.5 to 3 minutes. When one removes the contraption from the stove, the air in the bottom chamber starts to cool down. That creates vacuum, which sucks the liquid from the top chamber back down. The glass rod has an uneven surface, which acts as a filter, so no coffee grounds make it to the bottom chamber.
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| Air bubbling in the top chamber |
I learned the hard way that the coffee should not be ground super finely. One time the glass filter clogged up and the force of the vacuum broke the glass in the bottom chamber. Thankfully, a replacement was not hard to find. It took me a while, though, to formulate a guess (or should I say hypothesis) for what happened.
The resulting coffee tends to be very smooth and clean. I really like it that there are no filters to throw away. Most of all, the whole process is like a lab experiment and I always loved to do those. There are much prettier-looking siphons out there, and one day we will acquire one to appropriately wow ourselves, and our visitors.
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| Coffee back in the bottom chamber |
One of these days I intend to try pour-over coffee, which some say is the superior way of making coffee. But that will take the time as it seems that one needs to carefully experiment. Maybe coffee is not such a trivial thing after all :-)
Update, March 2022
I continue to roast our coffee and have settled on Sweet Maria's as my source. Ethiopian coffee remains my favorite. With our new oven I adjusted the roasting temperature to 430F (about 220C). I have replaced the syphon with pour over as the preparation method of choice. I use the water at 200F, and the coffee to water ratio of about 1:17 - for a gram of ground coffee I use 17g water. That may sound excessively finicky, but using a scale is quick, helps with consistency and predictability, and it also prevents me from overflowing my cup. The most significant upgrade has likely been the coffee grinder as I switched to 1ZPresso JX with a remarkable difference in grinding speed, uniformity of the grind, and of course coffee flavor.
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| A much improved coffee grinder |
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