The smell of freshly ground coffee is evocative, heady and indescribable, and in some ways it is worth paying for a coffee grinder for this alone. However, grinding your own beans at home will also make an enormous difference to the quality of your cup, compared to buying pre-ground coffee.
The aim of grinding the beans before brewing is to expose enough surface area to extract enough of the flavour locked inside the beans to make a good cup of coffee. If you brewed whole beans you’d end up with a very weak brew. The finer the beans are ground, the more surface area is exposed and, in theory, the faster the coffee could be brewed because the water has more access to it. This is important when considering how finely the coffee should be ground for different brew methods. The fact that the size of the coffee grounds changes the speed at which the coffee brews also makes it very important that we try to make all the pieces the same size when grinding coffee. Finally, grinding the coffee exposes more of it to the air, which means that the coffee will go stale more quickly, so it should ideally only be ground just before brewing.
There are two main types of coffee grinder available for domestic use:
THE (WHIRLY) BLADE GRINDER
These are common and inexpensive electric grinders. They have a metal blade attached to a motor that spins and smashes the coffee to pieces. The biggest problem is that this smashing action produces some very fine powder and some very large pieces. When you brew coffee ground like this, the tiny pieces will quickly add a bitter flavour to the brew, while the larger pieces will add an unpleasant sourness. This uneven brew won’t be very enjoyable.
Beans ground in a blade grinder (left) will be of a more uneven size and make a less palatable brew than those milled from a burr grinder (right), which has two cutting discs.
THE BURR GRINDER
These are increasingly common and available as electric or manual models. They have two cutting discs, called burrs, facing each other and you can adjust the distance between them to change the size of the grounds of coffee produced. Because the coffee grounds can’t escape until they have been cut down to the size of the gap between the burrs, the resulting grounds are very even in size. Burr grinders produce even pieces and an adjustable range of sizes, so they are ideal for brewing great coffee.
Burr grinders are more expensive than blade grinders but the manual models are relatively cheap and easy to use. If you enjoy coffee, it will prove to be an invaluable investment, especially if you are brewing espresso. However, because grind size is so important in espresso – variations of a few hundredths of a millimetre make a difference – it is important to buy a burr grinder designed for espresso with a good motor capable of grinding the beans very fine. Some grinders can grind for both filter coffee and for espresso, but most do one or the other.
Different manufacturers use different materials to make the burrs, such as steel or ceramic. Over time, the cutting teeth on the burrs will start to dull and the machine will start to mill the coffee rather than cutt it cleanly, producing a lot of tiny pieces that make the coffee taste flat and bitter. Follow the manufacturer’s recommendations for how often to change the burrs – new burrs are a small but worthwhile investment in your coffee-brewing setup.
Many people who enjoy coffee as a hobby like to upgrade their equipment from time to time. I would strongly recommend investing in a better grinder first. More expensive grinders have better motors and cutting burrs capable of a more uniform grind size. You will make a better cup of coffee with a high-end grinder and a small domestic espresso machine than with a cheap grinder and a top-of-the-range commercial espresso machine.
A burr grinder will cut beans into evenly sized pieces and can be adjusted to various grind sizes. They are an ideal investment for making a great brew at home.
DENSITY AND GRIND SIZE
Unfortunately not all coffees should be treated equally in the grinder. Darker roasts are more brittle in the grinder, and you may need to grind a little coarser.
Equally, if the coffee is from a much higher altitude than you typically drink – for example, you’ve been drinking a delicious coffee from Brazil, and then you switch to a coffee from Kenya – you may need to go finer in your grinder for the high-grown coffee. Once you’ve made the switch a few times you can make a well-educated guess when changing coffees, and prevent too many bad brews.
GRIND SIZE
Communicating grind size is not easy. Terms such as ‘coarse’, ‘medium’ and ‘fine’ aren’t particularly helpful because they are relative. There is no common setting among grinder manufacturers either, so setting one grinder to a numerical setting of ‘5’, for example, won’t replicate the grind of another grinder set to the same setting, even if it is the same model.
Below are some different expressions of grind size, with the accompanying photographs shown at life size. This should get you close to the perfect grind, then with a little experimentation each morning you should be able to achieve a much more delicious cup of coffee very quickly.
