In the past, we’ve looked at a dose in ratio and brew time. Today we’re looking at the most complex of the variables, which is the grind setting. How fine or how coarse you should be grinding the coffee, and when you should use your grind setting to make an adjustment to taste.
Espresso is a lot of fun, but it’s also immensely frustrating, especially when you’re starting. I would say this variable is by far the most frustrating of all of them to work with.
Is My Espresso Grind Too Fine?
Let’s say you make a grind setting change going a little bit finer. In doing so, you’ll expose a lot more surface area of the ground coffee.
If you think about cutting an apple into big pieces, there’s not that much surface area, but if you diced it down into tiny pieces, you’d expose a lot more of the inside of an apple, and the same is true with a coffee bean.
More surface area is very useful for extracting more coffee flavor, but when you change the surface area, you also change how the grounds interconnect with each other.
And when you tamp them down in your little pack of coffee, the finer the pieces are, the better they fit together and the harder it is for the water to flow through them. This will increase the contact time between the water and the coffee.
So you have this one chance to the surface area that impacts flow rate and contact time, as well, and that’s a bit of a headache. And then, quite often, changing the grind setting is a little bit wasteful for an extra twist.
This isn’t true of every single grinder ever made, but it’s very true of many, many, many coffee grinders people use for espresso. They don’t perfectly push out all of the coffee they grind every time you use them.
Inside the grinding chamber that houses the burrs as well as the exit chute, you’ll often find some residual ground coffee, and that was ground at a setting maybe before you made a change.
So when you make a change, you need to purge out some coffee to push out to these old grounds set at the wrong ground setting with some new ones.
And that’s frustrating because some grinders need a lot of purging and others don’t, but either way, that’s coffee that you never get to drink.
That’s coffee that you waste, and so changing the grind setting is frustrating, but it’s necessary.
Without grinding finely enough, you can’t do the extraction work that you need to get all the good flavor out using only a little water.
And that’s the kind of nature of espresso because you want to use just a little bit of water to have a strong concentrated thick delicious sweet espresso at the end of it.
People worked out pretty early on that to brew faster, and you had to grind finer. That way, this increased surface area meant that those flavors were more accessible, but quickly you get to the point where there was a problem.
Finely ground coffee is difficult to get water through, and in the early years of espresso, different methods were found to increase the pressure that the water was pushed through with the coffee.
Eventually, with compressed springs, we got to the pressures we use today, around nine pressure bars.
It’s equivalent in strange money of 130 psi, but ultimately it’s nine atmospheres of pressure. That is a lot of pressure that causes problems in espresso brewing.
Generally speaking, you want to go as fine as you can and expose as much surface area as possible before you break the puck.
Espresso brewing happens at these very fine pressures, and they are dependent on resistance coming from the coffee cake. But at some point, that very high pressured water may well find a channel through which to run an easier pathway.
And what happens when an espresso puck essentially breaks is that it begins to channel, and more water begins to flow through less of the coffee.
Channeling happens in most expressos at some point and to varying degrees. Still, as you go finer and finer and finer, you increase the channel forming likelihood because you created such a lot of resistance to the water pressure.
The grind is not the only variable that dictates how good a job your puck does of creating even resistance throughout the whole brew.
The puck’s depth will also play a role in your puck preparation and how evenly the coffee is distributed before you tamp it down. Often people will talk about over-extraction when you grind a little bit too fine.
I know I’ve done that too, and we associate that word with very bitter flavors coming through in your espresso. Generally speaking, the puck as a whole may not actually be over-extracted.
The puck as a whole may be under-extracted, but the areas around the channels where water has flowed much faster, and in higher volumes, they are extremely over-extracted.
So they’ve given up more flavor than we want, and they’ve added that bitter harshness to the shots, but you’d argue that more uneven extraction than it is over-extraction
Again, if you’re measuring this stuff with refractometers and looking at your total yields, you won’t see a big increase in extraction that incredibly fine grinds. You’ll see a drop.
In the past, this pushed people to experiment with a coarser grind than is typically used for espresso.
Should Espresso Be Ground Fine or Coarse?
I’m not going to say you have to use very coarse grains because you end up needing to use a higher ratio to get a more balanced shot.
But you do get a more even extraction using these slightly coarser grounds than you do use finely ground coffee, but your result does feel and taste and has a kind of different texture and strength.
How Should I Set My Espresso Grind Settings?
So let’s talk about using grind in a much more practical way. I would use grind to first and foremost get my flow rate about right. Let’s say I’m looking for 18 grams in, 36 grams out in around 30 seconds.
I’m going to use my grind setting to get me to that point. But once I’m there, I’m going to taste it, and chances are the tweaks I’m going to make if the espresso is good but not perfect will be two other variables that we’ll discuss.
If I’m still a long way away from good tasting, say I’m still very sour, I’m going to go finer again and see how that does, even if it’s outside of my original spec.
If I get my grind setting approximately correct, then I’m going to make those little tweaks with dose, with yield, potentially with temperature.
But primarily, I would suspect with my coffee in and my coffee out. They’re going to let me fine-tune that recipe pretty easily.
The reason I like to use grind like this for the big changes, but maybe not as often when I’m tweaking, is largely practical.
If you’re a beginner or intermediate in the world of espresso, then I think making fewer grind changes is probably an easier thing.
There’s waste from purging; there’s the general frustration around making those changes and making them accurately, especially if you have a new grinder or you’re just new to the process.
So I think big changes with the grind are good, and also, if you have a stepped grinder, where the steps between each setting are quite large, then I would probably go for the finer of the two, even if that means dropping down my dose.
I’m just more likely to have a good experience that way than being stuck with a slightly coarser grind than I might want.
If I lived in a world with unlimited coffee, unlimited time, and resources, I would use grind to make small adjustments, but that needs a very good grinder, patience, and quite a lot of waste.
I’m not sure that’s great real word advice or recommendations. So I would say you’re more likely to enjoy your espressos and the espresso-making process if you’re not throwing away a ton of coffee each time.
Should Espresso Be Ground Fine Or Coarse?
So at the risk of repeating myself use your grind to get close get a good-tasting espresso. If things are dominantly sour, you need to grind a little bit finer. If you’re finding things are getting a little bit too bitter and harsh, or you’re getting a lot of channeling, then maybe come back a little bit coarser.
To wrap up, I’ll give you a few simple rules to use when thinking about grind settings.
1. Once again, use it to get in the ballpark of taste. Fix your recipe, don’t vary that. Just use your grind setting to get to pretty good and then tweak from there using your other recipe variables.
2. Generally speaking, push it as fun as you can before you start to see channeling happening. Channeling will be very obvious if you’re using a naked portafilter, and you’ll start to see the uneven flow in your basket.
You will see this in the last third of the espresso, but you can also see it in the spotted portafilter.
You’ll be looking for a sudden increase in flow rate as coffee starts to gush out of their spouts in the last third of the chart, or potentially the last half if things have gone wrong.
Channeled espressos tend to taste a little bit weaker than you expect. It is a kind of hollow with acidity coupled with a bitterness that you get in the finish—a kind of harsh, biting aftertaste.
In the past, I’ve even recommended grinding from some grinders into a little collection chamber, bucket, shaking out any potential clumps, and then dosing into your portafilter.
Puck prep is really important but going too fine will produce channeling no matter what.
3. Only change one flow-related variable at a time. If you’re changing your grind, do not change the dose of coffee in your bucket simultaneously.
You won’t understand or get insight into the impact of either one that way, and you won’t know what’s gone right or what’s gone wrong. So if you’re changing your grind, keep everything else the same to understand the nature of the change you’ve made.
4. Purging is essential. It’s better to purge and waste five grams of coffee than waste the whole dose that you ground incorrectly.
So if you are changing a grind setting with most grinders, five gram,s 10 grams, it depends on the make and the model, but make sure you’re getting nothing but the new grind setting that you want to test to see if it makes the espresso that you want to drink.