Okay, I'll start. If everybody can add a bit of data, maybe Phil can assemble it into a readable, crystal clear FAQ to espresso for newbies!
1. What is espresso?
Espresso is commonly defined as 7g + 90°C + 9bar + 25s + 30ml. (with a 5% tolerance). This means:
7 grams of coffee
with water of 90 degrees Celsius
forced through the grinds at a pressure of 9 bar
in 25 seconds
to get a 30 ml. cup.
Note: a lot of coffee afficionados use a double filter basket and pull what is really a double ristretto: some 30 -40 ml. of espresso, made with 14 grams (or even more) of coffee, with the other variables unchanged (9 bar, 90 Celsius, 25 seconds).
2. What do I need to make a decent espresso?
An espresso machine that can deliver 9 bar of pressure on the grounds.
Ideally, a burr grinder (for these requirements, see "FAQ on machines").
Fresh coffee: roasted within a week of preparing the drink, freshly grounded.
3. How do I go about?
a. grind coffee
b. loosely overfill the filter basket
c. gently shake the filter basket to distribute the grounds evenly in the filter basket. If necessary, use your fingers or the back of a measuring spoon to distribute the grounds.
d. sweep off the excessive grounds (you can sweep them back into the doser if you will pull another shot soon)
e. knock the portafilter on your counter and tamp. Use some 20 pounds of pressure (practise with a bathroom scale if necessary).
f. remove any stray grounds from the portafilter: these will wear out your gaskets.
g. lock the portafilter.
h. press button / switch lever. The stream(s) from your portafilter should be thick and wobbly, and look like foamy honey. If your shot comes out too fast, grind finer. Do not try to compensate by tamping harder, as this is much harder to do.
Test your espresso by pouring a small spoon of sugar on the crema: it should stay on top of the crema for a while.
TO THE TMC MEMBERS:
If you have pictures of beautiful shots (or the steps of preparation) to accompany this FAQ, please send them to Phil. Additions and remarks are welcome.