High extraction espresso / How I make coffee

Posted on September 5, 2021

Method

Story

In early 2021, I watched a series of videos by James Hoffman on YouTube, and began doing experiments to achieve high extraction. After a few weeks of trials I settled down on this technique and has been doing it for more than six months now. The nice thing about this is that it gives good results every time. In fact it is quite hard to make a disaster even if some mistakes are made (like accidently using high pressure/flow)

The key idea for achieving high extraction is to have large surface area, which in turn is obtained by grinding the coffee very fine. But the finer the grounds are the higher is the chance of a disaster, as the grounds will either block the pores of the porta filter, or result in channeling due to high resistance of the puck.

The solution I devised is to let the coffee grounds absorb/adsorb moisture. Since the extraction of coffee happens by the flow of water over the grounds, if the grounds already have contact with the water it will enhance the flow of more water over it (while brewing).

To achieve this passive absorption of moisture, I keep the grounded coffee in small bowls, and keep these bowls inside another container which has little bit of water in it. If this container is kept closed (with a lid) the moisture inside it should reach a very high value after a few hours. The coffee kept in it for more than 12 hours should absorb upto 15% water by weight. Also the “volume” of the coffee grounds would increase. (When clamping the coffee you can feel it; the moisture rich grounds would occupy more volume for the same amount of pressure)

The other important point is to make the espresso slowly, maintaining a low pressure. Unfortunately I have a cheap “automatic” espresso maker with a rather high pressure. The way I achieve low pressure (and less flow) is by turning the machine on and off repeatidly (pulse width modulation). A manual lever machine would be very nice.