Coffee-grinding is a vitally important factor of excellence. Inappropriate coffee-grinding may mean that an otherwise excellent product is burnt while the coffee is being made.

If the ground coffee is too coarse, it loses solubility, which means the water can flow off without fully extracting the aroma and flavour. If too fine, the beverage is too strong and occasionally acquires the flavour of burnt coffee.

For an excellent cup of espresso coffee the ground coffee must produce 25 ml (± 2.5 ml) of beverage in 25 seconds (± 2.5 sec.).

If making the coffee takes more than 30 seconds (over extracted coffee), a coarser texture of ground coffee is required. If it takes less than 30 seconds (under extracted coffee), a finer ground coffee is required, to slow down the flow of water through the coffee.

The quantity of ground coffee per shot must range from 6.5 to 7.5 grams. The hopper and doser must be periodically cleaned. Clogging of coffee on the doser blade may affect dosing. Fatty clogging of the hopper or doser will make for rancid coffee.
The ground coffee should be consumed rapidly following grinding (max. 1 hour).