Barista course · Episode 3

Grind size — the most powerful adjustment

The full text of this episode — to read, look up and quote.

Cold open

Here are two little heaps of coffee. Same bean, same amount. One coarse like salt, the other fine like icing sugar.

And exactly this difference, the fineness of the grind, is the most powerful adjustment you have. More than any other, it decides whether your espresso tastes good or not.

Where this sits in the five Ms, and why

The third M, the mill. Why is the grind of all things so powerful? Because it controls how quickly the water runs through the coffee.

Picture the finely ground powder as a dense resistance. Grind coarser and the gaps are bigger. The water rushes through quickly, too quickly, and takes too little with it.

The result tastes thin and sour. Grind finer and the resistance grows. The water needs longer and dissolves more.

Go too fine and everything clogs up. The water struggles through, and it turns bitter. Your job is to find the point in between.

Chart: the grind scale

Picture a scale, from coarse to fine. Far left, coarse, as for the French press, where water simply runs through. Far right, dust fine, where almost nothing gets through any more.

Espresso lives in the right-hand third, in the fine range, but not right at the extreme. That is your espresso zone. And now the decisive part.

Your grind size is not a fixed value that you set once and forget for ever. A different bean, a new bag, another day with different humidity, and you adjust. The grind is the dial you turn most often.

So the rule is: coarser when it runs too slowly and bitter, finer when it runs too quickly and sour. Those two sentences are half your life as a barista.

Teaching: why evenness matters

Now comes the point where most people at home fail without knowing it. It is not only about how finely you grind, but how evenly. Imagine a few coarse lumps and a few dust-fine patches mixed into your fine powder.

Water is lazy. It always looks for the easiest way. It shoots through the coarse spots and drills itself a proper channel there.

And leaves the tightly packed rest almost untouched. That is what we call channelling. The consequence: one part is over-extracted and bitter, the other under-extracted and sour.

Both in the very same cup. That is why a grinder that grinds evenly matters more than almost anything else. There is an old barista saying.

Better to save on the machine than on the grinder. A middling machine with a good grinder beats the other way round almost every time.

Chart: types of burr

A quick word on grinder types, so you know what to look for when buying. Forget the cheap blade grinders with the spinning knife. They chop the coffee into uneven pieces, exactly what we do not want.

You do not take one of those. What you want is a burr set, two grinding surfaces that mill the coffee evenly. The flat burr is the most common and it is good.

The conical burr turns more slowly, stays cooler and so protects the aromas. And at the top end, for enthusiasts, the roller mill. The most even grind there is, but expensive and large.

For home use a solid flat or conical burr grinder is exactly right. No blade grinder.

Hands-on

Now you. And this is the most instructive exercise of the entire course. Set your grinder deliberately too coarse and pull a shot.

You will see it rush through in a few seconds, pale and watery. Then set it markedly finer and pull again. Now it drips, sluggish, dark and slow.

Taste them both. One sour and thin, the other bitter. And somewhere in between lies your point.

You do not have to hit it perfectly today. You are only meant to see with your own eyes and your own tongue how much a small turn of the grind moves.

Common mistakes

Three stumbling blocks. One. Saving on the grinder and putting the money into the machine.

Usually the wrong way round. Two. Grinding in advance.

Ground coffee loses its aroma within minutes. Always grind fresh, right before the shot. Three.

Turning the grind and something else at the same time. Only ever change one thing, otherwise you never know what did the work.

Recap and your task

Let us hold on to this. The grind controls the flow time and is your most important adjustment. Too fast and sour?

Grind finer. Too slow and bitter? Coarser.

Evenness is king. So get a decent grinder, never a blade one, and always grind fresh. Your assignment.

Turn it deliberately too coarse once and too fine once, and taste the difference. In the next episode you get to know your machine properly. From front to back.

omaneo — and YOU can do espresso.