#preinfusion

Pre-Infusion Video

Here is a video on Pre-Infusion that gives a little history on the different methods for achieving this. The oldest methods is in the manual lever machines and the E61 groupheads and the newest methods are achieve by way of gradual pump pressure increase in manual paddle machines like the LM Strada MP.

Although the video does not cover this much, I would add that the LM EP and Modbar are pushing the quality of pre-infusion even further by allowing programmable profiling, including different ways to ramp up and down the pressure.  

There is wide range of opinions on which method of pre-infusion is best and what is the best practice terms of amount of pressure and the duration of the pre-infusion. In the end, however, it is universally accepted that pressure profiling single origin espresso and higher quality espresso blends draws out more of the nuanced flavors. 

Manual Lever Espresso Machines (more photos)

There are seriously old school and Lo-Fi machines, the first true espresso machines, orginally designed in 1945 by Achille Gaggia in Italy.  They operate by using spring pressure to push the hot water through coffee grinds. Before manual lever was invented, steam-pressure was used which is so hot that it burns the grinds and does not have enough bars of pressure to qualify as actual espresso. In 1961 Feama invented the E61,the first motorized pump driven espresso machine, which is the most common type of machines in coffeehouses today.

However, the manual lever is making a comeback in artisan coffeehouse, because This is mainly due to the fact that these machines do a great job at preinfusion and pressure profiling, which has a great influence on the flavor extraction from freshly and lighter roasted beans. Some of the more famous 3rd-Wave coffeehouses using manual lever are Blue Bottle Coffee (SFO), Barefoot Coffee (SJC), Insight Coffee (SAC), and Cafecito Organico (LA).

A number of coffeehouses have refurbished classic La Marzocco manual lever machines, but a number of companies are still making them new. These include Victoria Arduino, Rancilio, Astoria, and La Povonia.