Turning the Pump On
Insert Portafilter and Immediately Brew
After inserting the portafilter into the group head, it is important to immediately begin the flow of hot water. Anytime dry coffee sits in the filter basket locked into the group it is heating up and absorbing moisture. The most consistent approach when preparing espresso is to press the brew button immediately after inserting the portafilter. You can place the coffee cups under the spouts after you hit the button, as there is a few seconds’ delay before the first drip of coffee leaves the spouts.
How to Use a Semi-automatic Machine with Presets
Semi-automatic espresso machines have a computer inside them helping them perform more consistently. To control the size of an espresso, the computer communicates with a flow-meter. This accurate method allows a machine to be programmed to dispense the appropriate amount of water, and the system is activated with a single touch of a button. Many machines have several buttons that can be programmed to brew any size of espresso you prefer.
A technician programming a semi-automatic machine to brew the correct size of espresso for a particular recipe uses a scale to measure the weight of the espresso shot. After the machine hits the desired weight, it remembers the amount of water that it dispensed when it was first programmed. Take care to be consistent with your dosing because the machine also takes into account how much water the coffee grinds soak up. For example, if you dose a little high, your coffee grinds will soak up a little more water. That means your espressos will end up a little smaller than you may want.
A video demonstrating volumetric control. This video demonstrates what happens if you dose too much coffee. You will notice some flashing of the LED displays on the scales and espresso machine. This is caused by the LED controllers in these devices clashing with the refresh rate in our DSLR cameras.