Espresso! My Espresso!
How a Pressurized or Enhanced Portafilter Works
by Randy Glass - Copyright 2009 - All rights reserved

      A questions that comes up from time to time is why are some machines equipped with a portafilter that is advertised as being "enhanced," or "pressurized." This article will try to explain what these are, their role in creating espresso, and whether or not you want one.

      Here is a diagramatic image showing a standard portafilter:

A: The brewhead- this is part of the machine itself, and this is where the water comes out when the brew cycle is started.
B: The Filter basket - normally made from stainless steel, this is the part that holds the ground coffee in preparation for making espresso.
C: The Portafilter Body - the part that has the handle attached that locks the assembly into the brewhead for making espresso.

Here's how it works:

1 - Hot water, is pumped by the machine into the portafilter.
2 - The water reaches the coffee and fills the space about the coffee. The very fine grind of the coffee as well as its being compacted resists the flow of the water.
3 - When the water reaches enough pressure to flow through the coffee (usually, or at least hopefully a pressure of about 130 psi or 9ATM) it dribbles out of the bottom of the filter basket.
4 - The espresso flows out the bottom of the portafilter body.

      To keep the ground coffee particles out of the cup, the bottom of a standard filter basket has lots and lots of tiny little holes. Each holes slows very little water, but all together, they allow a fairly free flow of water from the machine into the cup.

      If the user has filled the basket with a too-coarse grind, there will not be enough resistance to the flow of water and the espresso will be thin in body and have little taste, and can be quite bitter from under extraction. If the user uses a too-fine of a grind, the flow of water will be very slow and low in volume, and the espresso will be over-extracted and will taste sort of burnt and nasty. It will also be quite dark if a lot of fines (tiny particles) from the ground coffee end up in the cup.

      Once that resistance is created at the right level, the oils, colloids, and other elements are extracted from the coffee to create the ultimate coffee beverage. The bitter elements are still there in the coffee, but the other elements mask the tongue so that they are not tasted... when it all goes right, of course.

Here is an "Enhanced" portafilter:

      You see that its basic construction is much the same as the first example with one exception:

D: On the bottom of the basket, or possibly as part of the floor of the portafilter body, there will be some sort of flow restricter or pressure regulator. The design of these varies widely. It might be a rubber disc with a small hole in it or it may be a flat metal disc held by spring tension. Why is it there?

      These additions to the portafilter have one basic purpose. They slow the brewing process by creating an artificial resistance to the pressure. In the first example, the machine depends on the user supplying the coffee in a precise range of particle sizes by using a quality grinder carefully set to an acceptable grind level. In the enhanced portafilter the user can grind in just about any grinder and put it coffee ground in a wide range and still produce about the same results.

enhanced portafilter     The examples shown in the above images were diagramatic, created to help you understand how an enhanced portafilter functions. While the design of some enhanced portafilters is as simple as a metal or rubber disc with a small hole, others can be very complicated as seen here.

      The problem becomes one of the user not really knowing what is happening because the flow will be about the same regardless of the grind, coffee age, and amount of coffee used. Indeed, the water flow can be about the same through the enhanced portafilter even when no coffee is used.

      The other problem is that once the pressure is at a level that allows the enhancing device to flow water, the resistance to the flow is BELOW to the coffee and not necessarily in the coffee itself. In the standard portafilter it is the coffee that resists the flow of water. In the enhanced portafilter it is the enhancing device that often supplies the resistance, or at least a good portion of that resistance.

      In some of these the user cannot even tell by the production of the crema because the enhancement device will emulsify some of the coffee oils as well as mix in the air and gases present and create a sort of "crema-ish" topping on the coffee.

      So the answer to "why" is that these allow a home espresso making person to even use pre-ground coffee or use an "entry-level" grinder and still get a sense of what it takes to make espresso. Unfortunately they will seldom get a sense of what quality espresso tastes like.

      So making espresso using an enhanced portafilter can make things easier and even more economical, but often the results in the cup, and even more so on the palate, are disappointing when compared to a standard portafilter.