Grind and Tamping
The grind and tamping go together hand-in-hand. The idea is that the packing of the coffee grinds provides resistance for the heated water. This resistance causes the water to flow slowly through the grinds and extracting the components of “espresso” at the coffee-water interface. As well, this extraction pressure causes the gases (mostly carbon dioxide formed by roasting reactions) to pass into solution…forming the elusive crema–a sign of a good “pull.”
All other factors being equal, the finer the grind, the tighter the grains may be packed tighter. Also, the harder you tamp, the tighter the grains of coffee are packed together. These two variables together affect the amount of resistance afforded by the coffee against the heated water.
What you read about the grind from other sources is true. It is VERY important and not to be overlooked. Don’t even try using a blade coffee chopper. They are fine for normal drip coffee and French press but a chopper will not give you the narrow range of grain sizes for espresso. As well, if you manage to get one good grind with a chopper, it will be almost impossible to repeat it. At least get yourself a lower-end conical burr grinder (the La Pavoni PG are supposed to be good, and the Bodum Antigua I’ve used with success). Better still, get a dedicated espresso grinder (I now use a Gaggia MDF but like the Rancilio “Rocky” as well).
For my Gaggia MDF, the perfect grind is achieved at setting 5 or 6. The description of the proper grind range from grains that resemble sand to grains slightly coarser than flour. My feeling is that these guidelines are too vague and can mean something different to each person. That is, you can play around with the proper grind all day, but at this stage, it may be more effective to eliminate another variable and work on the tamp. For now, simply go to the nearest grocery store and find yourself a can of ground Illy regular roast espresso (something that should be easy to find worldwide) and you’re in business! You can always mess with the grind later.
Tamping is where I had my breakthrough. In order to get any crema, it is amazing how hard you actually have to tamp. I find that in order to produce an excellent shot, it was necessary to pack the 12 grams of coffee into the double portafilter with about 35 pounds of pressure. As you let off on the pressure, give the tamper a twist to polish off the top. The twisting also keeps any coffee from sticking to the bottom of your tamper. I tamp and polish twice.
To practice, put your handle and portafilter with the coffee on top of a bathroom scale and press down. Feel how hard this is for reference and practice, practice, practice! With the proper amount of coffee and tamping, there should be about 3-5 mm of space between the grinds and the top of the portafilter. If there isn’t, take a bit of coffee out or the handle won’t fit into the group head. That being said, there are some La Pavoni users that grind finer and barely tamp. After you master tamping the Illy pre-ground coffee, you can work on your own variation.