The making of the perfect espresso is an art form which requires considerable skill to master.
A good extraction is characterised by a 5-10 second delay before any coffee will pour. Heavy droplets will appear and develop into a thick, straight, and even pour. The colour will be dark and chocolate. The pour should be cut off before the colour lightens and the pour begins to curl in.
There are three main factors to controlling extraction:
The dose is the volume of grounds required in the coffee handle to produce the espresso. Machine handles have a reference line that the grounds, once tamped, should just cover.
There should be about a millimetre between the packed coffee and the shower foil. This allows the hot water to settle over the pack, thereby drawing out all the flavour and allowing enough room for the grounds to swell.
Too little coffee in the handle makes it too easy for the hot water to flow through. Hence, a lot of the good flavour in the grounds will not have been extracted.
Too much coffee in the handle makes it too difficult for the water to flow. Without room for the water to settle over the pack, the water will penetrate unevenly and the good flavour will not be extracted completely.
For the sake of freshness, every coffee maker needs to know how to grind to order:
Tamping is to apply firm and even pressure on the dose, using the metal implement called the ‘tamper’. The compressed dose offers resistance to the highly pressurized water about to settle on it.
Once you have developed a consistent dosing and tamping technique, extraction will be controlled by adjusting the grind setting.
The dry grounds should look like castor sugar – fine yet granular. Use the filter basket as a guide. The grounds should be slightly larger than the perforations.
If extraction is too rapid, the grind needs to be finer. If the extraction is too slow, the grind needs to be coarsened.
Be sure to make only small adjustments – just one notch on the adjustment collar at a time. Always remove the grounds in the old setting before adjusting.
Temperature, humidity, and the wearing of the burrs affect the accuracy of the grind setting. Adjustments need to be made to control the rate of extraction.