Few things are more enjoyable than a cup of perfect coffee. As coffee enthusiasts, we strive to achieve this ideal cup every time.
Sadly, many of us fall short of this goal. The coffee we brew at home is fine, perhaps even good. But it’s missing that special something that separates the average Joe’s cup of joe from a genuinely perfect coffee.
The secret to brewing the best tasting coffee begins long before water and coffee ever meet: it’s in the grind. Grind coarseness is particularly important when using a bean-to-cup coffee machine, as most models have multiple settings from fine to coarse.
Today, we’ll cover everything you need to know about grind coarseness, and how it affects the taste of your coffee.
Why is Grind Coarseness Important
From the coarsest cup of cowboy coffee to the finely powdered coffee enjoyed in Turkey, there’s a wide variance in the way coffee is ground. While some aspects of grind size boil down to personal preference, there’s also science behind why grind is essential.
There are many different ways to brew a cup of coffee, and while purists may spend hours arguing over the virtues of pour over vs drip, the truth is you can make a truly delicious cup of coffee with any brewing method, provided the proper grind is used.
The primary cause of a mediocre cup of coffee is over or under extraction of the coffee from the bean. Coffee that’s under extracted may taste weak, sour, or overly acidic, whereas coffee that’s over extracted often tastes bitter, burnt, or hollow. The coarseness of the grind allows you to control these factors to dial in the perfect cup of coffee.
Flow Rate & Contact Time
The size of your coffee grinds has a profound effect on the flow rate and contact time of your brew. Coincidentally, these two factors play a significant role in the flavour of your cup of coffee.
Flow rate refers to how quickly or slowly water travels through your coffee grinds. A high flow rate usually results in under-extracted coffee, whereas a low flow rate can lead to over-extraction.
Contact time refers to how long the water is interacting with your coffee grinds. If the contact time is too low, you’ll end up with under-extracted coffee. Meanwhile, if it’s too high, your coffee will be over extracted.
The key to the perfect cup of coffee can be found in finding the sweet spot with regards to flow rate and contact time, and the easiest way to adjust those parameters is with the size of your grinds.
Other Factors That Determine Taste
While grind size is one of the most critical factors in your quest for the perfect cup, there are some other concepts that play a role in the flavour of your cup of coffee. I talk about this more in my article on the science of brewing, but here’s a brief overview.
Temperature is one factor. Depending on the temperature of your water, the resulting cup of coffee will have a higher or lower extraction yield. Higher temperatures produce a more full-bodied and sweeter cup, although there’s a higher chance the resulting cup will be bitter and astringent.
Lower temperatures tend to produce a sourer and brighter cup with less bitterness and fullness to the coffee.
Coffee is typically brewed between 91 and 96 degrees Celsius, but small variations of your brewing temperature can profoundly affect the flavour of your cup. You may not have control over this when using a coffee machine, but it’s worth keeping in mind when you’re adjusting coarseness.
Aside from water temperature, the composition – including the presence of heavy elements – can also have a major impact. I’ve written about this here, so read that article to learn more (as it’s a complex topic).
The other factor in play is pressure. With many brewing methods, such as drip, pour-over, or immersion, the pressure isn’t a concern. But, with some methods, such as a percolator, espresso machine, or syphon brewer, the pressure will affect the results.
Increasing pressure will reduce contact time, which will lower the extraction of the coffee. Conversely, decreasing pressure will reduce contact time and raise the extraction rate.
Rules of Thumb for Different Brewing Styles
Your personal tastes will steer you in the right direction when it comes to how you grind your coffee, but there are some general guidelines you can follow to help you get closer to the perfect cup. It’s best to start with these guidelines and experiment from there so you can dial in the ideal coffee for your taste.
Cold brew calls for the coarsest grind possible. Since the coffee is extracted at or below room temperature with cold brew, the extraction rate is extremely low, and the extraction time is very high, as in 12-48 hours, typically.
Finer grinds will work equally well, but they’re usually much more difficult to filter out, making an extra coarse grind your best bet. Cowboy coffee also calls for an extra coarse grind.
Immersion brewers like a French press also call for a coarse grind, although not quite as coarse as cold brew. Coarse grinds work well with immersion brewers for the same reason why cold brew benefits from the coarsest grind; it’s merely easier to filter out the solids. While the popular Aeropress brewer is quite similar to a French press, these tend to work best with a medium-fine grind.
Drip coffee brewers, as well as percolators, are best served by a medium-coarse to medium grind size. Depending on your brewer, you’ll want to experiment with different grind sizes to determine the optimal size for your brewer.
A medium to medium-fine grind tends to work best with pour-over brewers. Your mileage will vary based on your particular model, but a medium grind is usually best as a starting point. If your coffee is under extracted, that’s a tell-tale sign that you need to up your contact time, which you can do with a finer grind.
Perhaps the coolest looking way to make a cup of coffee is with a syphon brewer, and these brewers tend to do best with a medium-fine grind. These brewers use pressure to force water into the chamber holding the coffee grinds. Once the coffee has steeped amply, heat is removed, and a vacuum is formed. This vacuum forces the steeped coffee through a lower section of the brewer, which filters out your grounds.
When making espresso, the contact time is concise, and it’s essential to maximise the contact time to achieve the most delicious flavour. The best way to do that is with a fine grind.
Finally, Turkish coffee is known for its exceptionally fine grind. It has the consistency of flour, and most residential grinders can’t even achieve such a fine grind, so special Turkish grinders exist solely for this purpose.
The Right Grinder for the Job
In your search for the perfect cup of coffee, you’re likely to invest in a quality grinder to grind your whole beans. There are two different types of grinders, burr grinders and blade grinders.
One type of grinder is a powerful tool for getting the most from your coffee, whereas the other is a paperweight with blades.
Burr grinders grind your coffee by sending the whole beans through two or more burrs, which crush the coffee into uniformly sized grinds.
Blade grinders don’t actually grind coffee; they chop it. Mostly, it’s a food processor for your coffee beans. Even the most expensive blade grinders can’t achieve the same level of uniformity as a cheap burr grinder.
If your grinds aren’t uniform in size, you’re effectively undermining the entire process, and all your hard work will end up going to waste. If you’re serious about producing the best cup of coffee possible, invest in a burr grinder.
Fortunately, (almost) all the best bean-to-cup coffee machines come with burr grinder. You can check out my list here: https://beantocupcoffee.co.uk/
Achieving the perfect cup at home is a labour of love, and it’s one that requires a great deal of trial and error as you refine your processes. While factors like temperature and pressure also play a role in the extraction of coffee, the easiest and most effective way to control the taste of your coffee is with the size of your grinds.
If you find that your home coffee isn’t the perfect cup you’ve hoped for, experiment with the size of your grinds, and you’ll be able to realise the ideal coffee for you.