Coffee Theory: Getting Started

The world of coffee is enormous. The strange devices, the seemingly endless regions (Guatemala Huehuetenango, anyone?), the flannel shirts and indie bands…it can be a little intimidating at first. Before talking about any specific coffee concepts (which I intend to do in the near future), I want to first introduce you to the bare essentials of good coffee. I would highly advise you to first address these in your home setup before proceeding: a well-prepared drip coffee will outclass any coffee from even the craziest of contraptions if the fundamentals are ignored.

On the next post, I’ll describe three user-friendly coffee techniques to apply these ideas. Once we have a firm grounding (lol) in the basics, we can move on to other fun coffee topics.

Fresh Coffee and Good Water
Not surprisingly, good coffee starts with good coffee beans and good water. I’ll focus on the former. Ultimately, good coffee (ignoring brewing techniques) relies on three things:

  • The original quality of the coffee before roasting. Unless you’re roasting your own coffee, this is up to whomever you purchase roasted coffee from.
  • The quality of the roast. Each coffee behaves a little bit differently—the different flavors present in your coffee may be more or less obvious based the roast. Lighter flavors, like berry in most Ethiopian Gujis, tend to show up best in lighter roasts. Darker flavors, like dark chocolate in some El Salvadors, might work better with a medium roast. Despite this variation, there are dead giveaways of sloppy roasting:
    • from-beans-your-cup-coffee-primer-w1456Over-roasted: extremely dark coffee tastes bitter and burnt and is usually only salvageable with prodigious application of sugar and cream. This mistake is the most common of the three—a large majority of people (myself included) are introduced to over-roasted coffee first, most notably through Starbucks.
    • Under-roasted: extremely light coffee tastes grassy and somewhat sour. This mistake is pretty uncommon at the commercial scale—it happens much more frequently with home roasters.
    • Nonuniform: If the coffee is not of uniform roast—i.e. you see many different shades of darkness—that’s a bad sign. It means they didn’t evenly heat the beans, and it mixes the worst of under-roasted and over-roasted. Like under-roasted, it is an uncommon mistake for commercial roasters, but very common for home roasters—roast uniformity can prove very elusive without proper equipment and significant expertise.
      A nonuniform roast
      • Note that this is distinct from coffee blends. A coffee blend is a mixture of coffee from multiple regions (as opposed tosingle-origin), either roasted together or roasted separately then blended. The latter case can be distinguished from nonuniformity by looking for “gaps” in the darkness gradient: if you can sort your coffee beans into 2-4 definite color categories, that’s probably a blend, but if it’s more of a gradient, it’s probably poorly roasted coffee.

        A blend
  • The age of the coffee. Most of the compounds that make coffee delicious are volatile, meaning it evaporates and diffuses away from the bean. This leaves the coffee bitter and stale. Your job is to get freshly roasted coffee and protect it fromlight and oxygen as well as you can.
    • Roast date: As a rule of thumb, most coffee is best enjoyed before two weeks past the roast date. There’s some leniency here of course (this flavor loss is a gradual process), but I typically stop hot brewing 2.5 weeks after roast date. Any coffee that old goes straight to cold brew, the most forgiving coffee brewing method (more on that in my next post).
      • Note: Immediately after the roast, coffee releases gas, primarily CO2, in a process known as “degassing”. This outgoing CO2 can create an uneven extraction (another term for the next post) which adversely affects the flavors in your coffee. The flavor magnitude of this effect depends on both the chosen brewing method and the amount of degassing, which is directly related to the time since the roast date. For example, degassing can ruin an espresso but leave a french press unaffected. The degassing phase mostly finishes within anywhere from 2-4 days after roast date (although there are extreme examples of coffees that don’t peak until as much as 11 days afterwards). I would advise you to simply chat with a barista from wherever you bought your coffee—they should have a good sense of how long to wait for a given bean and method. Or you could just experiment with it yourself and write down what you taste.
    • Storage: Keep the freshly roasted unground coffee in a well-sealed container and leave it in a cool, dark area (like a cabinet or something). I would advise against freezing coffee beans—while there are results that suggest freezing coffee can better preserve flavor and even improve grind uniformity (which is a critical factor), it is known that frozen moisture can destroy the structure of the beans, meaning if you fail to freeze them properly you will ruin your coffee. This is an article for the basics—let’s not get too fancy yet.

It’s worth mentioning that “good coffee” is a subjective term to some degree. Vietnamese iced coffee, for example, is traditionally made with massively over-roasted bitter Robusta beans…and it’s delicious (although it tastes awful without sweetened condensed milk). My grandpa loves over-roasted stale coffee—I’ve seen him repeatedly leave out a pot of coffee for days and continue to reheat it and happily sip away. It disgusts me, but hey, he doesn’t seem to mind. So if you prefer gas station coffee—go for it. Get year old preground coffee, crank up the water temp to boiling and let it stew for hours. Basically, just do the opposite of anything in this article. Anyways…moving on.

Grind Immediately and Grind Accurately
Remember how I said the stuff that makes coffee delicious is volatile, meaning it evaporates relatively quickly? Well, these compounds must diffuse out of the bean through its surface, meaning the rate of diffusion is controlled by surface area. Lower surface area to volume ratio = slower diffusion = better coffee for longer. Smaller particles (ground coffee) have a higher surface area to volume ratio, and thus allow flavor to float away at a faster rate.

Surface area to volume ratio
  • Grind Immediately: Buy your own grinder and store your coffee whole-bean. If you buy it preground, that surface area to volume ratio will be dangerously high, meaning a whole lot of those flavors will literally evaporate by the end of the day.
  • Grind Accurately: The same principle of surface area to volume ratio governs your coffee brewing as well—water can only extract coffee at a rate proportional to the surface area, meaning your grind size will dramatically affect the extraction of your coffee. There’s lots to talk about here (Matthew Perger does an excellent job of explaining extraction), but I’ll just say this: your goal is to get the coffee ground as uniformly as possible, with an average particle size corresponding to the coffee method (e.g. fine coffee = espresso, medium = drip, coarse = french press).
    Blade grinders are terrible—the only control over the distribution of particle size you have is how long you leave the grinder running. It’s like trying to get regularly sized shards of glass by repeatedly dropping a flower vase—at each phase, the average shard might get smaller, but you’ll have all sorts of sizes, ranging from glass dust to big ol’ daggers of glass. You cannot evenly extract coffee from a bad distribution of grind sizes.
  • Burr grinders are the standard. Good grinders can get expensive, so here’s a great table of grinders.
Picture credit to

Dose Correctly: Get a Scale
Finally, the simplest part of good coffee: correct dosage. If you want consistently high quality coffee, a scale is absolutely critical. I mean, you could spend years honing your ability to estimate masses of coffee…but I want good coffee now, so…

All you need is a scale that’s precise to the gram with a capacity on the order of ~2 kg. Coffee bean size and density varies greatly, so weight is the gold standard for measuring quantities (this principle also holds in cooking…weight is far better than volume, people). Water density, on the other hand, is fairly uniform and the approximation of 1 mL ~ 1 g of water is typically good enough for coffee applications…although there’s nothing wrong with using a scale again here. Pourover, for example, practically requires that conversion.

Regarding recipes for different methods—I will post three user-friendly brewing methods soon (within a month). I want to talk about them in a little detail and compare the relative merits of each. For the time being, Stumptown and Intelligentsia both have excellent brew guides for many methods.

There’s already a lot of stellar material out there for a growing coffee geek (Matt Perger’s blog, Reddit’s r/coffee, CoffeeGeek …). I highly encourage you to continue exploring. Perhaps the best thing you can do is go to your favorite local coffee shop and just chat with the baristas—trust me, they love coffee and should be excited to help you get started. Ultimately, you learn by tasting, experimenting, and listening to those farther along in their coffee journey. Good luck, and may your coffee be delicious.

Coffee: A habanero mocha at Provision Coffee in Gilbert, Arizona. Habanero has a wonderfully fruity flavor in addition to all that heat, and it can be difficult to balance in a drink—but Provision did an excellent job. Not pictured, their Ethiopian Guji is also delicious.

One Comment

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  1. Nice! Hope to see more! 🤗☕☕😬


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