If you're shopping for a coffee grinder, chances are you're pretty meticulous about your coffee (or have at least taken the first step onto that slippery slope). For our grinder testing we've done everything in our power to match that level of meticulousness. We divided our tests into four different metrics: grind consistency, cleanliness, user friendliness, and noise.
A good coffee grinder gives your beans the best chance of fully expressing themselves, and it does that by creating a very consistent grind size. If a grinder leaves too many large chunks of bean, also referred to as 'boulders', it leaves less surface area touching the water. This leads to under extraction, and a weak tasting brew. On the other end of the spectrum, creating too much coffee dust (often dubbed 'fines') leads to over extraction and bitterness. The more grinds that fall into that middle sweet spot (the exact size of which will vary depending on your specific brew method) the better your coffee is going to be. Because grind consistency is so important to the end result of your coffee beans, it was our most involved testing metric.
Coffee Bean Selection
For all of our tests we used single-origin beans, meaning all the beans were of the same origin and roasted in the same way. While coffee blends are quite popular and can be quite delicious, they are by definition a mix of different types of beans. Therefore you can get slightly different results from batch to batch depending on the exact ratios of the different components that end up in your coffee scoop. Using single-origin beans for our tests eliminated this variable.
This is our most direct test of grind consistency. For this test we ground 10 grams of coffee on a pourover-sized setting with each grinder. We then put those grounds through a 4-tier set of sieves (size 46, 40, 30, and 23 OPN). The more of the grounds that fell into that ideal 23-30 OPN ideal size range, and the fewer that ended up at the extreme ends of the spectrum, the better the score.
This test gave us a more functional examination of grind consistency, meaning it allowed us to quantify how closely each grinder was able to get to ideal brewing standards. Using a classic Hario V60 and the standard [Stumptown pourover guidelines, we first saw how easy it was to dial in the grind size of each machine to reach the ideal pourover extraction time (the time from first pour to the last of the water making it through the filter, including a 15-second break to let the coffee bloom) of 3 minutes.
Once we had everything dialed in, we then made three pourover cups with each grinder, carefully timing the extraction of each. We then calculated the variation in those extraction times, with wider variation indicating less grind consistency from cup to cup, and tighter time indicating better cup to cup consistency.
Pourover asks for a medium sized grind, so in this test we looked at how well each model handled larger grind sizes (French press) and smaller sizes (espresso).
While some of these grinders can actually perform reasonably well as espresso grinders, most just barely reach the largest grind size that could be considered appropriate for espresso. We simply used their espresso settings to see how well they perform at the finer end of the spectrum, and we generally wouldn't recommend using these grinders in conjunction with an espresso machine.
In testing grind consistency for French press sizes we redid the sieve test. This allowed us to easily quantify how many grinds ended up in the ideal size range, and how many fines (the bane of a good French press brew) were actually produced. For the much finer espresso grind the sieve tests would be less meaningful, so we simply pulled multiple shots of espresso instead. We then timed the extraction for each shot, noting both how close to the ideal 30ish seconds each grinder could reach, and how consistent the extraction time was between shots.
Consistency matters not only in grind size, but in grind amount as well. If you tell your grinder to make 21 grams of grounds, but on Monday that ends up actually being 25g, and on Tuesday it falls short to 17g, you're going to be far less effective in that Tuesday morning conference call.
To test dosing accuracy we ground what the grinders said should be the same amount of coffee three times over with each device. We then weighed out each dose to see how similar they actually were. We repeated this test for multiple different grind sizes.
Of course we imbibed after brewing all of this coffee, having everyone from our in-house barista and caffeine addicts to, "I only drink coffee when I'm tired," type folks do some tasting and weigh in on each cup's relative attributes. However, we didn't use these taste tests in our scoring because we still believe producing a consistent grind is more indicative of a grinder's ability to make a wide variety of coffees taste good than subjective taste tests ever could be. That being said, almost to a T all of our taste testers far preferred the coffee made with the models that scored highest in our grind consistency testing.
As you can tell from our grind consistency testing, we ground lots of beans with each one of our grinders. This gave us plenty of opportunity to evaluate the messes (or lack thereof) created by each model. In ranking cleanliness we focused on two things: static and shrapnel. If a grinder creates a lot of static you'll end up with the fines sticking to the cup or other surfaces, making it somewhat hard to clean and to get all of the coffee into the brewing vessel of your choice. Also, some grinders tend to shoot grinds outside of the grinding cup (coffee shrapnel, if you will) creating a mess both on the body of your grinder and the counter. We ranked all of the models in our cleanliness metric based on how many issues they had, and to what degree, in these two categories.
Most of our user friendliness testing focused on each device's interface. Through repetitive use by multiple testers we evaluated their intuitiveness, general design, and how easy it was to dial in the preferred settings every morning. We also assessed how easy it was to disassemble the actual grinding components for general cleaning, and how clear the manufacturer's instructions were in walking one through that process.
In evaluating how grating the screeches of all these grinders were we started with an objective test: measuring each models' maximum volume using a decibel meter placed 2 feet away from each device. However, at this point we've learned from experience that the volume of a sound is only a small part of what makes it annoying, what's more important is the pitch. Therefore, we also had multiple testers subjectively rate the relative aggravation induced by the sound of each model. We made sure to run these tests using multiple different grind size settings, and as each model ran out of beans (some let out a scary screech when that happens).
In putting together this review we believe we've created the most objective, repeatable, and exhaustive testing process possible. We genuinely hope that our coffee nerdery has helped you figure out exactly which grinder to adorn your countertop with.