What is Pre-infusion?
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.
Pre-infusion on the LUCCA A53 Mini
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 (instructions are available below 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.
Pre-infusion on the Direct Plumb A53
Pre-infusion on the plumbed A53 model can be programmed 0-8 seconds. Because water line pressure is feeding the machine, the brew solenoid opens for the desired number of seconds, allowing water to flow through passively without activating the pump. After the pre-infusion time is met, the pump activates for the remainder of the shot.
Programming pre-infusion on the A53:
With the machine on, hold down the power button for 5 seconds until "95", the power light, and the "boiler" light are blinking.* This is programming mode.
*Note: If your coffee boiler is set to a higher or lower temp., that is the number that will be blinking, i.e. a boiler set to 90 will be blinking on "90", power light and boiler light.
From programming mode, hold down the "B" (boiler button) for 5 seconds until the number is not blinking but the boiler and power light remain blinking. You are now setting the length of pre-infusion. Each number, 85-ECO, represents 1 second of pre-infusion time, i.e. 95 is 3 seconds of pre-infusion.
Tap the boiler "B" button until the desired number of seconds is displayed, indicated by all the numbers lit up from 85 to the setting you selected (85-your setting will be lit).
When you are satisfied with the number of seconds, tap the power button to exit out of programming mode and back to normal function.