The Science of Coffee
Like an inchworm, we humans are constantly measuring. And not just marigolds either. As I write this, it is not yet 8 am and I have just finished pouring 700 milliliters of water over 45 grams of coffee as reported by my trusty kitchen scale. The water was the perfect temperature of 98 degrees Celsius, and I recorded in my journal this morning that it is a bright blue spring day and a crisp 5 degrees C. Earlier, I stepped on the scale and washed my hands for 30 seconds. Later, I will go for a run and measure my distance, time, pace, heartrate and a bunch of other stuff my Apple Watch tracks but I don’t pay attention to. (Quick! What is a VO2 Max?)
You too measure stuff all day long. Even if you don’t make your coffee with the kind of obsessive attention that I do, you still measure, at least by instinct and habit using estimates that have been honed over a lifetime of experience. The units we grew up with are ingrained, and like most systems learned at an early age, they are hard to change.
About ten years ago (appropriately enough), spurred on by a love of baking and a desire to “be the change you want to see in the world” (falsely attributed to Ghandi), I decided to go all metric, all the time. Let me explain.
The thing that started it was bread. Peter Reinhart, in his book called The Bread Bakers Apprentice introduced me to the idea of “baker’s math.” Baker’s math sounds scary, but it is a simple system for replacing recipes with formulas that makes it possible to scale a bread recipe to any quantity you wish. Baker’s math works by expressing all the ingredients as a percentage of the weight of the flour, which is usually the main ingredient. So, if, for example, you know that in your formula you have 600 grams of flour and the weight of the salt is 12 grams, salt is 2 percent. If you increase the flour to 800 grams, now the salt must be 16 grams. While the formulas will work just fine with imperial measures, the math is much easier with the metric system (Quick! How many teaspoons in a quart?).
The second advantage of baker’s math is even more important – consistency. Flour is easily compressed. It can be packed into a cup or it can be sifted and contain a lot of air. The result is that when baking by volume measurements (cups, tablespoons) the amount of flour in a cup will vary changing the way the dough behaves from batch to batch. With weight the quantity of flour is exactly right every time. Again, using the metric system makes it easier.
The origins of the metric system date to the French Revolution in the late 1700s. At the time, an estimated 250,000 different units of measurement were being used in France! I don’t even understand how that is possible, but it made commerce and trade challenging to say the least. Bread was sold using one unit, cheese by another, wine by yet another. The metric system was designed to be rational and universal across commodities. Even so, there was tremendous public resistance and took a long time to take hold. When the nascent United States of America was establishing its system of measurement in the early 1800s, the metric system was still not catching on in France. Going with Great Britain’s imperial system seemed like the safer bet and more familiar to the former American colonialists. Today, of course, Britain, like almost every other country in the world, uses the metric system. In fact, there are just two other countries in the world besides the US that don’t use the metric system – Liberia and Myanmar.
So when I decided to switch to the metric system for baking, I asked myself, what was stopping me from using the metric system in other aspects of my life? There were two obstacles.
The first is that I wasn’t used to it. There would be mild discomfort as I struggled to relearn what was reflexive.
The second was that no one else around me was using it. My insistence on the metric system in writing, practice, and everyday conversation would likely bewilder, even irritate those around me. Upon further consideration this seemed more like a plus than a minus.
The switch was easier than I thought it would be though there were some hiccups.
Mass/Weight: In everyday life we don’t weigh stuff that often and I was already using a scale for baking. Switching from ounces and pounds to kilograms was easy.
Length: Also, fairly easy. We use metric measurements for length surprisingly often in the US. Athletic events are often delimited in meters and kilometers, from the 100-meter dash to the 5K fun run. But in everyday life, people use inches and miles (Quick! How many inches to a mile?) If someone asks you how far something is and you tell them in kilometers, they look at you funny. Speed limits can be a concern but most cars still have an analog speedometer that displays miles per hour and kilometers per hour on the same dial. And who cares about speed limits unless there is a camera or cop?
Volume: Wine and liquor are sold in 750ml bottles for some reason. Milk, however, is packaged in gallons or divisions thereof. Beer is usually sold in 12-ounce cans or bottles as is soda. But the large bottles of pop are sold in liters. Huh?
Temperature: My switch to Celsius for temperature was probably the most irritating for my family and friends. My kids would ask me what temperature it was, and I would respond in Celsius. But they got used to it, eyerolling not withstanding. Really, temperature is the easiest because how often do we need to know temperature exactly? Precision is only required if you have a fever or are cooking chicken. Here is a Celsius primer. 0 = freezing, 10 = chilly. Get your jacket, 20 = warm. 30 = hot. I’m schvitzing over here. 40 = bloody hot. Death Valley in summer hot. 100 = water boils. Salmonella is dead at 75. This is all you need to know.
Switching to metric, I changed the settings all of my devices to metric units. This is not as simple as you might think. On the iPhone for example, there is no master setting that changes all the units from imperial to metric. The default units are based on the country you pick when you set up the device. I tried setting my country as Canada but that caused other problems. I had to go into virtually every app and change the preferences.
After 90 days, I was no longer converting kilometers to miles or kilograms to pounds in my head. I just “knew” what they were. Now, ten years on, I use and think in the metric system 95% of the time. The questioning looks are just an opportunity to evangelize.
There are a few areas, however, where I still have not completed the transition and still use or think in imperial units.
Body weight. My bathroom scale is still set for pounds. I know how much I weigh in Kilograms but I still think about it in pounds. Body weight is one the most personal of numbers and hard to redefine in your mind. When I was growing up, I knew an elderly lady who was born in Scotland in the early 20th century. She still measured her weight in “stone” even though she’d been in the US for many years.
Fuel economy. In the US gasoline is sold by the gallon and cars are rated by miles per gallon. When shopping for a car or checking the fuel economy on one’s own car at the pump, it is just more practical to use mpg as a comparison number.
Hiking. Virtually every trail in the US and the USGS topographical maps are marked in feet and miles. Having to do conversions in your head while making sure you know where you are headed seems unwise and unsafe on a wilderness hike. When in the backcountry, I set my GPS for miles to match the maps and the trail signs. Safety first!
Cooking. I can’t figure out how to switch the oven thermostat to metric!
So, my journey continues as does the journey of human desire to measure and quantify. In fact, the metric system itself is incomplete and still evolving. The original plan for the metric system included a ten-based way to measure time. The scheme called for the adoption of a day which would be composed of 10 hours each of which had 100 minutes and further divided into 100 seconds per minute. Each week in turn was to have a length of ten days instead of seven resulting in a Sabbath only about 36 times a year instead of 52 times a year. The churches of Europe, which would have experienced a 30 percent drop in collection plate revenue, naturally opposed this change as did the working person who would have had fewer days of rest. In all likelihood, humanity won’t adopt a decimal calendar until interstellar travel becomes commonplace. (“Captain's log, stardate 41153.7. Our destination is planet Deneb IV …”)
In other ways, however, the metric system continues to advance. Just two years ago, for example, the Kilogram was redefined. Previously, the Kilogram was defined as the mass of a chunk of platinum known as Le Grand K that lived in a vault in France. It had served as the standard for the kilogram since 1889. Why the change?
Well, first of all, it was super inconvenient to have to travel to France every time you needed to calibrate your kitchen scale.
The second problem is more significant. According to Wikipedia “Beyond the simple wear that check standards can experience, the mass of even the carefully stored national prototypes can drift relative to the international prototype of the kilogram.” In other words, the mass of the damn things change over time! Not much, perhaps the weight of an eyelash over 100 years but for scientific purposes (if not for making coffee) such a small change is important and can really screw up your calculations. If you are trying calculate a trajectory through hyperspace from say Tatooine to Alderaan, you could end up on Mustafar instead. Awkward? At best!
So in May of 2019, the Kilogram, like the meter before it, was redefined to be based on a naturally occurring constant and Le Grand K is now just an antiquated hunk of metal destined to be auctioned off at Christie’s to some collector for a fabulous sum.
The important thing is that you no longer have to go to France to find out what a kilogram is. This is great news because I don’t think France is admitting Americans right now. But one day international travel will again be possible and when it is I am looking forward to enjoying 100 ml of Bordeaux and some stinky cheese with crusty bread at a nice café on the Seine.
When that will happen depends on when we can get vaccinated. I will certainly get mine as soon as I can. As everyone knows, a gram of prevention is worth a kilo of cure.