Espresso Blending
In this article: Espresso blending, coffee blend, arabica espresso, espresso robusta
"Good espresso comes from blends"
The world of espresso beans and roasting styles is hard to cover in whole, and the possible espresso blends are infinite. This article will not cover details, but will give you a few tips that will get you going with espresso blending.
The first rule in espresso blending is trying, trying and trying again. And take notes. Take notes on the relative amounts of beans (or ground coffee) used in every blend, and also take notes of your experience when drinking a cup from each blend. This way, you can experiment with blends over time and eventually find a few blends that are right just for you.
Also remember that there is no right or wrong. The professionals have ideas or "rules" on how to blend espresso, but don't be to religious - find the blend that you like the best.
What beans to use then? A basic rule of thumb for espresso blending is to use a mix of both Arabica and Robusta beans. It is generally considered best to use more Arabica than Robusta. The Arabica bean has a light touch while Robusta is considered "heavier" and with more bitterness. Robusta also gives the espresso more crema.
Most Italian espresso blends contain a mix of both Robusta and Arabica beans, while American blenders tend to use less, if any Robusta. An article at INeedCoffee suggests a mix with 10% Robusta beans.