Pre-infusion is the low-pressure soaking of the coffee bed before an espresso machine builds to its full 9 bar brew pressure. This settles the coffee puck, which can minimize channeling and improve shot consistency.
The A53 Mini uses a vibration pump, which builds pressure gradually and creates a very forgiving cup in its standard configuration. Pre-infusion can be increased to a fixed six seconds (non-adjustable) on the A53 Mini with an optional chamber that is installed at Clive. Or you can follow our instructions for installing or removing this chamber at home. Instead of the pump pressure flowing straight through the group head into the coffee, the pre-infusion chamber diverts some of the flow to create a more gradual ramp to full pressure. One thing to keep in mind is that installing the pre-infusion chamber can increase the sound while pulling shots, and increase the brew pressure gauge oscillate as it builds pressure. When your shot is finished, the brew pressure and pre-infusion chamber's water are diverted into the drip tray through the relief valve.