How to Make Espresso

Ideally, espresso should be extraordinarily sweet, have a potent aroma, and flavor similar to freshly ground coffee.  The cream would be dark reddish-brown.  It would  be smooth, yet thick.  A perfect espresso would be enjoyable straight with no additives, yet bold enough to not disappear in milk.  A pleasant and aromatic aftertaste would linger on the palate for several minutes after consumption.

Now I will discuss the various factors and problems with espresso that limit its potential and describe how you can maximize the espresso potential.  If any of these factors are off the espresso potential will be limited.

1. Blend - Without a good espresso blend you cannot have a good espresso.  Coffees must be blended to achieve the sweetness, aromatics, and smoothness desired in espresso.  The blend must also be fresh.  We recommend using espresso within four days of roasting. Order some excellent espresso blends from Neighbors Coffee.
 
2. Roast - Too often you will find espresso roasted very dark.  This results in a bitter, charcoal tasting brew.  People that know how to blend espresso will roast light to preserve the aroma and sugars.  More information.
3. Grind - The grind must be continuously monitored throughout the day to achieve an extraction time of 25-30 seconds.  Do not change the pressure you tamp with to compensate for a grind that has become too large or small.  More information on grinding.
4. Grinder - A high quality burr grinder is essential for espresso.  A conical burr grinder is preferred to flat burrs since the particle size is more even, they last longer, and the coffee is not heated during the grinding process.  If the burrs become hot the aroma of the coffee will be diminished.  A conical/parallel hybrid blade is considered the best design by many coffee professionals. 
5. Dosing - Coffee must be freshly ground to achieve peak flavors.  Grind and dose on demand.  When someone orders an espresso grind only what is necessary for one shot, dose properly, tamp, and brew.  Discard any espresso grounds that are not used within 30 seconds. 
6. Distribution - Distribute the coffee evenly after dosing in the porta-filter before tamping.  More information.
7. Tamping - Tamp the coffee once very evenly with 5 lbs of pressure, then once with 30 lbs of pressure, and polish 720° with 20 lbs of pressure.  More information.
8. Water mineral content - The water used for espresso must be filtered.  Some cities must even compensate for the mineral content of their water.  Over time oxygen will be forced out of the water in the espresso machine leading to off tasting water.  Try filling a small glass with water, letting it cool, and tasting it for off flavors.  If the water tastes strange you may want to dump the tanks daily and begin with fresh water.
9. Water temperature - The water temperature should be stable and somewhere between 92-96°C.  The choice of the espresso machine is very important to both water temperature and temperature stability.
10. Temperature stabilizing - A stable temperature means consistent espresso.
11. Water pressure - The pressure of the water forced through the espresso should be between 9 and 10 atm.  This pressure is responsible for the development of the cream.
12. Boiler pressure - The boiler pressure determines the amount of water to be incorporated in the steam.  If your milk is not foaming correctly as described in milk texturing you may want to experiment with different boiler pressures, but this should only be altered by professionals.  You can check your boiler pressure by looking at the boiler pressure gauge on the front of most espresso machines.
13. Extraction time - Extraction time to fill two 1-oz cups should be between 25-30 seconds.  Despite the time the pump should be turned off if the espresso becomes slightly lighter in color.  The goal is to have a dark red espresso take approximately 25-30 seconds to brew with no change in color.
14. Porta-filter and basket - The porta-filter should always remain the same temperature as the water used to brew the espresso.  Therefore it should always remain in the group head.  The basket should hold 16-18 grams of coffee and must be straight walled.  Curvatures in the basket will lead to uneven extraction.
15. Timeliness - Act quickly, but carefully.  You should spend no longer than 30 seconds for the time it takes to dose, distribute, tamp, pre-heat, and brew the espresso.
16. Espresso machine cleanliness - This is probably the biggest problem with espresso today.  If the machine, basket, and porta-filter are not cleaned regularly the espresso will always taste rancid. 
17. Espresso grinder maintenance - Everyday the burr blades should be swept clean.  Between shots you may want to brush out the excess espresso that gets stuck between the burrs and the dosing chamber.  The burrs must be replaced at least yearly so that they continue to produce coffee granules with a maximal surface area.
18. Environmental Factors - The humidity and temperature will change throughout the day.  Since coffee is hydroscopic (absorbs moisture), the grind size must be changed throughout the day to achieve a brew time of 25-30 seconds.  The temperature will not affect the espresso like the humidity, but it is important to avoid exposing the coffee to any high temperatures until brewing.
19. Espresso cup - The espresso cup should be pre-heated from a source other than the espresso machine.  Filling a cup with water from the espresso machine prior to brewing the espresso will lower the temperature of the water in the boiler and the espresso extraction will be uneven.  The espresso cup should have thick walls and a narrow mouth to retain heat and aroma, respectively.
20. Practice - I cannot overstress the importance of practicing and experimenting.  The key to espresso is to realize that it always has further potential.  By changing any one of these factors you can improve or diminish its potential.  Espresso preparation is an art that demands the precision and dedication of science.  I have never achieved, nor have ever seen a perfect espresso.  A perfect espresso more of a concept than an actuality.  The beauty is that espresso is volatile and difficult.  If it were easy we would develop a machine that can brew a perfect espresso every time.  There are so many factors involved in espresso preparation that only a human mind and a passionate heart can begin to understand and control its complexity.