There are a few common misconceptions about espresso. I once believed that a bag of espresso beans could only be used for an espresso machine. I also believed that espresso beans had to be dark roasted and oily.
Let's talk about what makes espresso espresso. Espresso is simply a condensed cup of coffee produced quickly at a precise tempature and under pressure. Espresso is a brew method that creates a condensed cup of coffee.
You can grab any bag of coffee beans and brew espresso with it, it may not be awesome though! Imagine you are taking the flavors of a cup of coffee and magnifying them. If you start with a lemony acidic coffee, you will have an especially lemony acidic espresso. How about a Rwanda with and underlying fruitiness or a murky leathery Sumatra. What might those taste like pulled as espresso? So when selecting beans for an espresso it's important to understand how they will taste in a "magnified" state. This helps to explain why blending for espresso is so popular. Some beans are perfect as a single origin espresso, but many good beans are missing a component or maybe have a little too much, say acidity, and need to be balanced out with another bean.
The roast does not determine whether beans are espresso beans or not. In the coffee world an "espresso roast" is generally understood to be a darker roast but this doesn't have to be the case. My eyes were once opened by a lovely Brazil Sierra Negra bean with a medium roast and brewed into a lovely clean espresso. Why has espresso generally been seen as a dark roast? My guess; because espresso is Italian. Have you seen an Italian Roast lately? It's practically black. If espresso had been invented in Sweden it would probably be a different story.
Here is where espresso begins in my opinion, for the consumer anyhow. As I roaster I am thinking about espresso when I select green beans for certain charactaristics of body, acidity and flavor and develop the roast profile that shows them to their very best. Anyone who has talked coffee with me for any amount of time will hear me go on about grind. Thats because after quality of beans, grind is the next thing most people can easliy perfect. Grind determines how the water will flow through the coffee grounds and how much flavor it will extract. As a general rule- the longer the contact time; the coarser the grind. Ergo espresso is a fine grind (20 second extraction) and Frech Press is a coarse grind (4 minute brew time), Cold Brew is whole beans (overnight steep time) just kidding, but I had you for a second. My point is if you have a course grind you aren't making espresso.
This! This is what actually makes "espresso" espresso. All of that other stuff before we even got to the shots is what I as a roaster worry about, THIS part is where I generally turn things over to you. Obviously, I pull shots to try my single origins and components for espresso blend potential and also for my own enjoyment but I am not going to go into bars of pressure or water tempature and crema here. The purpose of this article was to clear up what does and does not make something espresso.
Espresso may be enjoyed as is or added to a milk beverage. One espresso may be more suited to being enjoyed as a shot whereas another espresso might have the backbone that will stand up to dairy applications. An espresso that can do it all is especially exciting! I highly recommend you grind up whatever you've got and see how it behaves as espresso. Experiment! Learn! Bounce off the walls!