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Fundamentals of Espresso

**Extraction = Amount of coffee material that dissolves into water during brewing.

Factors that affect extraction are:

Grind Size, Brew Time, Water Volume Used, Temperature, Pressure, Humidity

In this short guide we’ll discuss how to achieve the right extraction with espresso brewing. Finding the sweet-spot where the espresso is most balanced, needs the above mentioned factors to be understood. Espresso machines push water at boiling point – 97°C, through a puck of coffee at 9 bars of pressure. This equates to a huge amount of energy being applied to the coffee – way more than is necessary to extract the soluble materials out of the ground coffee. Coffee is quite easy to extract because it has already been roasted at over 200°C. Due to this fact, it is also incredibly hard to burn with water that is only 97°C – however, it is very easy to OVER-extract. This means that you have extracted unwanted flavors by over doing the espresso brew.

In order to NOT over-extract your espresso you have to make a few changes:

~Reduce volume of water pushed through coffee puck.

~Reduce amount of time the espresso brew takes.

~Reduce the temperature of the water if possible.

Grind size is important to mention here because it is the back bone of espresso.

The grind size dictates how fast or slow the brew will take. The reason why espresso is brewed so fast is because the coffee is ground so fine. However, the finer the grind the more resistance there is to water flowing through the bed of coffee. If the grind is too fine then you will get channeling, whereby the coffee puck breaks, causing uneven flow and over-extraction.

So to achieve the necessary changes mentioned above, you will need to adjust the grind size. Most likely having to make it coarser, allowing for the water to flow through the group head faster. One more note on grind size that you need to be aware of is humidity. Humidity is an extra layer of resistance that slows down the espresso brew. Humidity changes throughout the day depending on the weather outside. You have to make gradual adjustments to your grind size during the day to account for this. You will know when to adjust and by how much, by timing and weighing your shots.

Also note that when you adjust grind size, you must keep the other variables constant, i.e.

~ Coffee Dose (Amount of coffee used)

~ Volume (Espresso yield in the cup)

Our recommended recipe for all our medium roasts:

Dose = 18g – 20g

Espresso Yield = 30 – 40ml

Brew time = 15 – 20 seconds

This is based off extensive testing, roast profiling and cupping. We reduced the volume of water used in a typical espresso of 50-60ml. Not only to reduce over-extraction, but also because the body/ texture/ mouthfeel is SIGNIFICANTLY affected! At 50-60ml, the espresso becomes very watery, lacking the full body/ mouthfeel that most enjoy.

We also reduced the brew time in order to prevent further over-extraction. We concluded that anywhere from 10 seconds to 20 seconds, (depending on pre-infusion time), is more than enough time for an espresso machine running at 97°C and 9 Bars of pressure to extract the most deliciousness from coffee. This will vary with levels of roasting i.e. Light roasts. If the espresso shot is run too long, 30-40s for example, then a bitter/ harsh after-taste develops. It is somewhat dry or astringent and lingers in your mouth long after the coffee has been drunk. Another result of over-extracted coffee.

Lastly, let’s talk – STRENGTH. One of the most common mistakes cafés and coffee lovers make.

Strength is NOT bitterness.

~ Bitterness is a result of poorly brewed coffee.

~ Strength is a result of how much coffee to how much water/milk has been used.

We call this a strength ratio. I.e. 1 : 2 or 1 : 4 (The lower the ratio the stronger the drink).

An espresso has a strength ratio of 1 : 2 , generally.

A cappuccino has a strength ratio of 1 : 5 (40ml espresso : 200ml Milk)

A caffe latte has a strength ratio of 1 : 8 (40ml espresso : 320ml Milk)

If you find that your drink is NOT strong enough then you need to change the strength ratio. Many cafés resort to buying “stronger” coffee beans or buying a darker roast. This is erroneous.

For example, if your caffe latte is too weak, reduce the ratio to 1 : 7.

40ml espresso : 280ml Milk


Change the ratio of your ESPRESSO. Use more coffee.

Change from 18g to 20g or even 22g.


Don’t change the volume! Changing from 30ml to 50ml will make your espresso over-extracted.