Coffee must be ground to be brewed. Grinding breaks the coffee into smaller particles. The smaller the particles, the more oils can be extracted within a set period of time. If two same weight portions of ground coffee are brewed, the finer ground portion will offer more flavor. When coffee is ground, it exposes surface area. The finer the grind, the more surface area is exposed. In this way, grind is simple.
But is it simple? The basics of grinding are simple and straightforward. In reality, grind is a complex subject because even the best ground coffee is inconsistently ground. If you look closely at these portions of ground coffee, you will note there are various sized particles. In a perfect world, they would be identically sized. But, they cannot be. There is a range of particle sizes and that’s against our best interests as coffee drinkers. Very tiny particles will extract too quickly, offering bitter notes even in a relatively short extraction time. Coarse particles never give their all, remaining underextracted. Yet the industry realizes that impracticality of consistency because the various grind sizes recommended for different brewing methods’ contact times always states a range with the expectation of various sized particles.
Here are some grind specifications for some popular methods.
- Drip grind – The drip grind dwells between a percolator’s eight minute coarse grind and a fine vacuum brewer’s four minute grind. Most drip makers ideally extract over a six minute contact time between water and grounds. In reality, the drip grind is the most important to get right, since the grind affects not only exposed surface area, but acts as a flow regulator controlling how fast the water takes to travel through the grounds. If you’re a wee bit off in your grind, you’ll get a double whammy of slowing/speeding the contact time and exposing more/less grounds surface to the water. In a three-to-four minute brewer such as Bunn makes, the preciseness of grind is even more critical. One reason this brewer gets underrated in brewer surveys such as Consumer Reports is the testers appear to misunderstand grind. With this brewer, using a slightly finer-than-normal grind and/or higher throw weights are optimal.
- French Press/Percolator – Interesting, how a grind standard designed to hold up for an eight minute percolator extraction works (apparently) equally well for a four minute French press extraction. The marriage between French press and coarse grind was obviously one of convenience, no doubt designed in response to the metal screen filter and its inability to travel smoothly through finer grinds. What happens in reality (seen in my Coffee Brewing Secrets DVD) is people up compensating for the coarse grind and short extraction time by using a heavier does of coffee. Jim Reynolds, French press expert, threw in a whopping 57 grams (which in a drip brewer would be a six cup measurement) for four cups. That works out to 15 grams per six-ounce cup, 50% higher than normal.
- Espresso – Espresso coffee is often considered its own animal, yet from a grind perspective, it is actually a super-fine drip grind, one designed for very short extraction times. The shorter the extraction time, the more critical is the grind, as variations are magnified. Virtually no espresso machine manufacturer offers a companion blade grinder for espresso machines.
Blade v Burr v Roller
Blade grinders are doomed to failure because they are known in the grind world as attrition grinders. This means they hit the beans repeatedly to break them into successively smaller pieces. Burr grinders are also attrition grinders but the blade has an additional challenge as it hits bean pieces pretty randomly as they are tossed around the grind chamber. The burr at least has gravity feed holding the beans roughly in place for it. The best option is a roller where beans are fed into it and where one pass allows the beans to be crushed between two rollers. Roller grinders are only available for commercial use at this writing.
Do Different Beans Grind Differently?
Different types of beans take to grinding differently. So-called soft beans, often have more moisture content. They are more difficult to grind consistently. So-called hard beans are easier to grind for the same reason in reverse. Those who store their beans in freezers will find that freezer-to-grinder results in a better grind due to the brittleness of the beans regardless of what kind. Even if there’s moisture, it’s frozen and ice chops nicely. Dark roast beans are often more brittle and this results in improved grinding characteristics, all other things being the same. Decaf also grinds differently.
All blade grinders are, in my opinion, out of the question. They do such a poor job, I honestly consider a preground coffee rather than grinding beans. I’m sure some of you will recoil in horror that I say this, yet I honestly think the tradeoff is that great, especially after testing so many poor grinders. And, no blade grinder has ever come close to acceptable.
Sadly, most consumer disc or burr grinders are not much better. Their consistency among the ground particles is often poor. However, even the worst burr grinders achieve a decent batch to batch consistency. They also are able to grind at least a full pot’s coffee without heating up as all blade grinders do, which releases flavor you want to save for your brew. I continue to test home grinders, albeit slowly because I do so objectively and that requires a test that can only be performed at a laboratory. Modern Process Equipment has advanced laser analysis apparatus that can effectively measure the exact capability of each grinder, but the process is time consuming.
One option is to find a decent commercial grinder. I own a small commercial Ditting grinder. I found it at a used restaurant supply house. Even with as many tests as I perform, I’ve owned it nearly 15 years and its burrs are hardly worn. Bunn, Grindmaster and Malkoenig are well regarded commercial grinders. If you shop carefully you might be surprised at how affordable they can be. The space issue might be a different story. Even my small (by commercial standards) Ditting grinder is too large for my kitchen, and is relegated to the garage.
Another option is to buy commercially ground coffee, or grind it yourself at your coffee dealer using their commercial machine and store it tightly packaged in your freezer. While this might seem a step down from your own grinder, if you can’t get a good one, I’d consider it.
Grinding is the one part of brewing that is proven to be objective.