Grind Size: It's Complicated

Regardless if you’re a home barista or an experienced industry professional, you probably already understand that grind size is an important factor in your brew. Most of us have noticed that grind size affects not only the strength of a brew - but also the actual flavours in the cup!

Why is that really? Today we’re going to dive deep into the subject of grind size!

What is grind size?

Most of you are probably familiar with different grind sizes, which can be sorted into coarse, medium and fine grind, but it’s not that simple.

First of all, when coffee is ground the powder consists of hundreds of thousands of particles and the size of these particles will be determined by the grind size you set on your grinder. With that said, no grinder in the world can give the same grind size on all the particles…

Instead, a grinder generates a ‘’peak grind size’’ which is the size that the majority of the ground coffee particles will have, but there will always be a portion of the ground coffee that is bigger than the desired grind size called ‘’boulders’’. On the other side of the spectrum, ground coffee also consists of particles that are smaller than the desired grind size called ‘’fines’’.

This means that no grinder actually gives you one consistent grind size, but instead gives you a mix of completely different grind sizes covering the entire spectrum from ultra-fine to coarse.

So there’s no point in even caring about the grind size, right?

WRONG!

Entry Level vs High-End Grinders

You see the difference between a high-quality grinder and a lower-quality one is the distribution between the fines, the “desired” grind size, and the boulders. This is called Grind Size Distribution. A higher quality grinder will give a more uniform grind, meaning that the ground coffee will have a higher amount of the desired grind size, a higher ‘’peak’’ and fewer fines and boulders.

Compare this to a cheap grinder, which generates a larger portion of boulders and fines and a lower ‘’peak’’, meaning that it generates less of the desired grind size.

This makes it very complicated to communicate grind size because all grinders have very different particle distributions.

To give an example, the term ‘’medium grind’’ doesn’t say much since it’s such a wide spectrum of grind sizes that constitute a ‘’medium grind’’.

Therefore it’s very difficult to realistically communicate grind size with a number… unless we sift the ground coffee or use a particle analyzer...

But let’s be honest, none of us will bother to sift our coffee and measure it for 30 minutes, and even fewer of us would pay thousands of euros to get our hands on a particle analyzer to find out the particle distribution of our coffee!

For those of you who DO want to measure the particle distribution of your coffee, here’s an app that lets you do that, completely for free! For those of you who want to unleash your inner coffee nerd, the app is called "Coffee particle size distribution" by Jonathan Gagne! 🤓

Few of us have the time to use complex tools like this, so let’s get back to reality. The good news is that there’s actually a very simple way to communicate grind size without communicating grind size. Can you guess what that is?

No, it’s not a number on a grinder

And no, it’s not a visual look on the ground coffee 👀

⏱️ The simplest way to communicate a grind size, is with the brew time

Brew Time

You see, the total brew time (both filter coffee and espresso) tells us tonnes about the grind size since the grind size affects the resistance of the water through the coffee - speeding it up or slowing it down.

To create more resistance (and increase the brew time), coffee needs to be ground finer to create more surface contact between coffee and water. To create less resistance (decrease the brew time), the coffee needs to be ground coarser to create less contact between the water and coffee

This is why you’ll often hear baristas say ‘’What’s the brew time for this coffee?” If you try the same recipe, but the brew is very fast, then it means you went too coarse... and vice versa, if you use the same recipe and the brew went too slow, you ground too fine!

So, next time you ask for the grind size, you should rearrange your question and ask: 🙋‍♂️‘’ What’s your brew time’’?

-P.T.

---

The Brew Journal is a twice-weekly email newsletter that helps you brew better coffee at home in 5 minutes or less. Join our growing community of coffee lovers who are levelling up their coffee game at home - sign up link below 👇