Espresso Size and Strength
In 1948 Achille Gaggia invented the lever espresso machine, and modern espresso was born. The new espresso was much stronger than previous iterations of espresso because the pressure produced by Gaggia’s machine was many times higher than that of earlier machines. The big increase in pressure also produced crema for the first time on espresso shots. This foam has become so valued by customers that it is now universally unacceptable to serve espresso without crema.
Note: The coffee oils in espresso cause the bubbles in crema to break up quickly. When you are preparing a set of drinks for a group of customers, make the straight espresso drinks last. This way, their crema has less time to break up.
Converting Espresso Volume to Mass
Let’s establish a formula for converting traditional espresso shot volumes into beverage weights. Crema has very little mass compared with its volume. It is mostly made of carbon dioxide gas. Thus, a beverage volume can be converted into a beverage weight by reducing it by 25% ±10%. For example, a 20-ml espresso might weigh between 13 g and 17 g.
A traditional Italian espresso tends to be brewed with lower doses than what is common in specialty coffee shops. One very strict definition can be seen here from the International Organisation for Standardisation (ISO). The ISO Standard 45011 describes Italian espresso as follows:
Dose = 7 ± 0.5 g
Liquid = 25 ± 5 ml
Beverage weight = 16–21 g
There is considerably more variation in recipes in the specialty coffee world, and recipes are usually expressed in terms of double shots.
Dose = 20 ± 6 g
Liquid = 50 ± 20 ml
Beverage weight = 35 ± 15 g