Roasting coffee beans

My daughter asked me yesterday whether I’d thought about roasting my own coffee beans. I told her no, that I thought that for whatever reason people didn’t often roast coffee beans at home, but I didn’t know why.

Today I asked an expert about this, someone who roasts and distributes coffee. He said that you can roast coffee at home, but most people don’t for these reasons.

  1. You can roast coffee in an ordinary oven, but the quality of the roast will be uneven.
  2. You can buy a machine for roasting coffee beans, but these machines are expensive and don’t roast much coffee at a time.
  3. It’s hard to find green coffee beans unless you are buying in wholesale quantities, e.g. 100 pound bags.
  4. The smell is overwhelming.

The last point surprised me. I imagined the smell of roasting coffee beans would be wonderful, but apparently it’s too much of a good thing.

Update: See the comments for different views and suggestions.

Related posts:

AeroPress coffee

People have been telling me to try an AeroPress for a long time, and I finally gave in. The deciding factor was that the AeroPress is entirely plastic and presumably unbreakable. When we broke yet another glass beaker in our French press, I decided it was time to try an AeroPress. (Next time I buy a French press, I think I’ll get one made of metal or shatterproof plastic.)

Compared to a French press, the AeroPress is faster to use and easier to clean. The taste is different, somewhere between the taste of French press coffee and espresso. This isn’t surprising since an AeroPress is somewhere between a French press and an espresso maker. Like a French press, you pour hot water over the grounds. Like an espresso machine, you use pressure to extract oils from the coffee.

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A tip on using a French press

When I first bought a French press, the instructions said to pour hot but not boiling water over the coffee. They were emphatic about what the temperature should not be, but vague about what it should be. (Boiling water extracts oils that you’d rather leave in the grounds; water a little cooler brings out just the oils you want.)

I asked someone online—sorry, I don’t remember who—and he said that after your water boils, set the kettle off the burner and check your mail. When you come back, the water should be at the right temperature. That turned out to be good advice.

I don’t know whether he meant postal mail or email, but it doesn’t make much difference. Unless you get caught in replying to email and come back to room-temperature water.

Now if you really wanted to geek out on this, you could use Newton’s law of cooling along with the surface area, thickness, and material composition of your kettle to compute the time to let your water cool to 200 °F (93 °C). You could assume a kettle is a half sphere …

Related post: A childhood question about heat

French press photo

A tale of two espresso machines

This post tells the story of two espresso machines: one in Los Angeles and one in Brenham, Texas. But it’s more about deciding what you do and do not want to control.

* * *

In his book Made by Hand, Mark Frauenfelder chronicles his quest to make great espresso at his home in Los Angeles. He reviews some of the tricks to make good espresso from a relatively inexpensive espresso machine. (The machine he describes, a Rancilio Silvia, was around $500 when Frauenfelder bought it. That’s a lot more than a Mr. Coffee, but it’s cheap compared to espresso machines that cost over $10,000.) The problem with inexpensive espresso machines is that they have poor temperature. The water temperature can vary as much as 40 °F. Frauenfelder hacked his espresso machine by replacing its controller with a more sophisticated proportional-integral-derivative controller or PID.

(Small changes in brewing temperature can have a large impact on coffee taste. This is because coffee is chemically complex. Brewing at different temperatures extracts these chemicals in different proportions. See this Scientific American article for details. [Update: looks like SA took the article down.])

The context of Frauenfelder’s story is his book on doing things yourself, not to save money, but to have more control of your environment. He describes his adventures from growing vegetables to making musical instruments for the joy of doing so.

* * *

Roger Sessions tells a very different story about why he does not have his own espresso machine in The ObjectWatch Newsletter. He describes why he drives 10 miles every day to the Starbucks in Brenham. He says he saves money, even though he spends more on gasoline than the price of his doppio macchiato. For starters, Sessions estimates it would take nearly four years to pay off his hardware investment. Then he lists the things that could go wrong:

  • Something might break down.
  • Something could short out his electrical system.
  • The roaster could burn his house down.
  • He might not be able to use the equipment well.

The context of Sessions’ story is the benefits of software as a service. Even when it appears to be more economical to create and host your own software, you may save money by paying someone else to offer that software as a service. Sessions pays Starbucks to make his espresso for him because they not only make the capital investment in hardware, they’re also responsible for operation and maintenance. (Update: See Roger Sessions’ comment below.)

* * *

Sessions makes as strong a case for not owning an espresso machine as Frauenfelder makes for owning one. Frauenfelder speaks of the confidence and joy that comes from having detailed knowledge and control of the things around you. Sessions speaks of the hassle and expense of being responsible for the things around you. Both have valid points. I’m sure there are areas in which Frauenfelder is happy for someone else to take responsibility, and areas in which Sessions enjoys fine-grained control. But they disagree which approach is preferable when it comes to making espresso.

One of the things that prompted me to buy Mark Frauenfelder’s book was an interview I heard on a podcast. He said that he was attracted to do-it-yourself projects after becoming editor of Make Magazine. The spirit of the writers rubbed off. At one point in the interview he says DIY is not about saving money; in fact, the DIY approach will often cost more money. I appreciated this comment since many DIY enthusiasts justify their projects with dubious financial arguments rather than simply say that they enjoy what they’re doing and that the extra expense is worth it to them. I suspect Frauenfelder may agree with Sessions on the economics of espresso making, though they have different perspectives of the non-monetary benefits.  And although Sessions only argues monetary benefits, he also has non-monetary benefits to visiting Starbucks. I imagine he enjoys getting out of his house, seeing familiar faces, etc.

* * *

Posts quoting Mark Frauenfelder:

Endless preparation
Getting women to smoke

Post quoting Roger Sessions:

Three quotes on software development

Four mechanical devices better than their newer counterparts

Here are four mechanical devices I prefer to their modern counterparts.

French press. It makes better coffee than a typical coffee machine. Also, a French press work without electricity. Next time a hurricane comes through Houston and knocks out our power, I can still make my coffee.

Reel mower. I had gasoline powered lawn mowers until last year. Sometimes they’d start, sometimes they wouldn’t. My reel mower always starts. And it’s quiet.

Rake. I had a leaf blower once. It was obnoxiously loud and a nuisance to my neighbors. I much prefer raking leaves even though it takes longer.

Pencil sharpener. With four children, we sharpen a fair number of pencils. We have owned a couple electric pencil sharpeners. They were noisy, hard to use, and soon wore out. Our mechanical pencil sharpener is cheaper and far more reliable.

I’m no Luddite, but I firmly believe that newer isn’t necessarily better.

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A little coffee on the prairie

I was reading Little House on the Prairie with my youngest daughter the other day. Here’s a passage that surprised me.

Then Pa brought water from the creek, while Mary and Laura helped Ma get supper. Ma measured coffee beans into the coffee mill and Mary ground them.

I’d read this book with my other children and hadn’t given this part a thought. This time I thought about how odd it was that they had coffee. At this point the Ingalls family was moving from Wisconsin to Kansas some time in the 1870’s. The family of five and all their worldly goods were packed into a covered wagon. They shot wild game for food. They gathered water from creeks. And yet they had coffee.

Coffee doesn’t grow in the continental United States. It grows in the tropics at high altitudes. These settlers living off the land in the middle of nowhere had some coffee beans that had been imported from thousands of miles away. It’s interesting to think that despite all that they lacked, they had these tropical beans and apparently took them for granted. Said another way, of all the benefits of civilization, coffee made the short list of things settlers chose to take with them.

Distribution of time customers spend in coffee shops

How would you model the time customers spend in a coffee shop?

This post is pure speculation based on no hard data whatsoever, which makes things considerably easier! If anyone has data or suggestions, please leave a comment. Here goes a first attempt.

The time people spend in a coffee shop depends on why they are there.

  1. Some grab their coffee and go.
  2. Some are there to visit with a friend.
  3. Some drink their coffee (alone) and leave.
  4. Some are there to work.

Each group would have its own time distribution, and the overall distribution would be a mixture of these distributions. Since I’m doing this for fun, I’ll ignore (1) and (2) and just concentrate on (3) and (4). I’ll also ignore complications such as how patterns change throughout the day and how they change according to the day of the week.

Say someone comes in alone to have a cup of coffee. Maybe they stay an average of 15 minutes. I’ll assume the time these folks spend in a coffee shop is normally distributed. Not many stay more than 30 minutes, so let’s say the standard deviation is 5 minutes. That would put only about 0.4% staying longer than 30 minutes. It would be more realistic to truncate the distribution at zero to eliminate the small probability of spending negative time in the coffee shop (!) and  skew the distribution a little to the  right, giving more probability to people staying more than 30 minutes.

The people who come to the coffee shop to work stay considerably longer than the folks who are just there to drink a cup of coffee. And their time distribution would be heavily skewed. These folks are unlikely to stay less than 30 minutes, so the distribution would drop off sharply on the left. There’s a wide variety of how long people might work, so I’d expect a long tail to the right. The inverse gamma distribution fits this description. Say there’s a 5% chance that a worker will stay less than 30 minutes, and a 5% chance they’ll stay more than two hours. Using this software to solve for parameters, we find a shape parameter of 6.047 and a scale parameter of 317.3 fits the time distribution in minutes. This distribution has a mean of about 63 minutes, which I suppose is reasonable.

Here’s what the graphs of the two distributions would look like: a symmetric distribution centered at 15 minutes for the drinkers and a skewed distribution centered around 63 minutes for the workers.

Now suppose 70% of customers are drinkers and 30% are workers. Then the mixture distribution would look like this.

As the percentage of workers goes down, so does the second hump in the graph. If a coffee shop had about 20% drinkers and 80% workers, the two humps would be about the same height.

How would you include people who come to a coffee shop with a friend?