[image-1]First of all, understand that pressure is what makes a cup of espresso earn its namesake. Get it? "Es-press-o." In other words, grind the heck out of your beans (espresso-grind), ultra-fine, so that when you forcefully push pounds of pressure through them, the liquid can extract the "crema," or emulsified nectar that is espresso. Exit drip coffee, where hot water flows leisurely through a relaxed crowd of ground coffee beans. The filter in a regular drip coffee-maker is going to blot your oils, where much of coffee's real flavor lies; use a french press to make a decent cup of regular coffee and avoid this.
Second, emulsification, or the process of rendering a new and wonderful chemical substance through the forceful incorporation of fat in to water (see properly emulsified salad dressings for a great consistency that does not separate), produces a cup of espresso. Nothing else. And emulsification in espresso-making only happens when the contents are under proper pressure and the water is forced through tightly packed, finely ground, coffee beans.
So there are two talking points to keep in mind here:
1) The GRIND is what makes a bean ready for "espresso"- and it must be super-fine for the water to be pressed through properly.
2) PRESSURE is productive of espresso; nothing else.
The roast of the bean has absolutely nothing to do with whether coffee beans will make a cup of espresso. This is a common misconception. Rumor has it that Italian immigrants to the US burnt the heck out of their coffee beans, because the coffee quality was so low here one hundred years ago, to mask the flavor. Over time, people began mistakenly referring to darker brews as "espresso roast."
Pressure is absolutely essential to produce the crema, or honey-nectar that is real espresso. This is why decent espresso machines run upwards of $500. Coldly elegant brushed steel, or weirdly whimsical pastel and curves, European espresso machines tend to be constructed with an eye toward design, but mostly you are paying for the machine's ability to produce the correct amount of pressure, measured in bars.
Pump-driven and 15 bars are said to be the most basic requirements for a machine to extract this beverage. The word on the street is that the average $100-ish big-box espresso maker does not produce the correct amount of pressure. A decent home-machine begins at $500 and can easily run in the thousands. Now you see why. More advanced models will grind and tamp your beans for you, lower-priced versions simply produce the pressure, and ask you to do these other tasks yourself.
And tamping, or pressing espresso-grind beans properly before brewing, is an art form in itself. Now you understand why the barista truly is a skilled position; there are rules, and skills, at play here.
But coffee-lovers everywhere abound and can put in their two-cents on how to make a decent cup of espresso, as well. [image-3][image-3] lists can be extremely helpful in learning what others have spent countless hours researching.
The bottom-line? You may not produce your own espresso drinks at home (you can have an espresso bar loaded with all kinds of fancy extras and entertain your friends making fancy coffee drinks in lieu of the traditional alcohol bar). But you should know what you are drinking, and talking about, when you visit your local coffee shop. Remember: ES-PRESS-O...... not EXPRESS-O.
Ian Finn, when he is not schooling people on proper coffee etiquette, writes cookbooks for the culinarily challenged.