How to grind coffee

By Emily
May 18, 2016

Here I share tips to help you master the grind.

One of the key points was the importance of the grind in controlling extraction, and the importance of good extraction for a balanced and tasty cup. Here I share tips to help you master the grind. Around 30% of the coffee bean is water soluble although it is has been analysed and is widely agreed with in the industry that only 18–22% is desirable in the cup. Leaving the other influences on extraction aside it is easy to appreciate that the longer the brewing water is in contact with the coffee the more solubles will be released whilst at the same time the finer the coffee is ground the greater the surface area and so the quicker the solubles will be released. This helps to explain the very important difference in grind between:

Fine grind – soft to touch with some grittiness
Brews in 20 – 30 seconds

Ground medium fine – table salt
Brews in 1-2 minutes

Filter / V60 / Moka Pot
Medium grind – caster sugar
Brews in 3-4 minutes

French Press (Cafetiere) / Clever Dripper
Coarse ground – granulated sugar
Brews in 4-5 minutes

In espresso and filter methods the grind also influences contact time. So being able to adjust your grinder is even more important. Here I use an analogy of ‘pebbles and sand’.

Diagram of fast flow vs slow flow depending on the coarseness of the grind.

Pebbles – too coarse, under extracted Sand – too fine, over extracted

If you are now grinding your own coffee. Being able to visually recognise a good grind for your brewer is a great starting point. Providing you have invested in a good quality burr grinder, whether that be electric or hand, you can easily make adjustments.

Flat burrs from an electric grinder

The burrs are held firmly in place facing each other within the grinder and rotate at speed to grind the coffee. The gap between the burrs, will be roughly the size the coffee is ground down to before it exits the grinder. For an even extraction we need a grind that is as uniform as possible with a minimal amount of ‘fines’ (dusty particles). Grinders with blades that chop up the coffee will not achieve a uniform grind in the same way. When we make changes to the grind we are moving the blades closer together (finer) or further apart (coarser) simple! It is usually indicated on electric grinders how to do this and on hand grinder it is a simple as tightening or loosening the nut that hold the blades together

Collar of an electric grinder with adjusments

Dialling in is the term we use to make adjustments to the grind that ensure we achieve a good extraction. As mentioned 18-22% is our goal but unless you are armed with a refractometer and extract mojo software you are unlikely to know for sure that you are in this golden zone…. It basically comes down to taste. Natural acids are released very easily during brewing and therefore extract first.

Nut of a hand grinder

Under extracted coffee will be watery and sour. Caffeine is also released early on so at the same time under-extracted coffee can be bitter. As we over extract, taking too much from the bean, bitterness overwhelms the brew.

Please note that coffee is naturally bitter and a gentle bitterness is pleasing like an olive or grapefruit. Acidity can also be pleasing like a crisp white wine. Sometimes achieving the perfect extraction is termed as ‘hitting the sweet spot’ drawing out and maximising the natural sweetness of the coffee whilst balancing bitterness and acidity without the extremes of either.

It is helpful to understand a little HOW do we taste. There are over 5,000 taste buds located within our mouth, each with different receptors: bitter, sweet, salt, acidity and umami. When we taste coffee the bitterness, sourness and sweetness combine with the aroma notes to give us the coffee flavours we know and love. Whilst the tongue itself is rather blunt only detecting specific tastes, our noses allow us to detect the myriad of nuances which helps makes everything we eat and drink distinguishable. If any of these receptors are over stimulated it can be pretty unpleasant. In coffee we are looking for balance of flavours, coupled with a rich mouthfeel (body) and complexity resulting in an all round delicious experience.

With the right grind you are well on the way to brewing delicious coffee wherever you are.

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