I made my first espresso on a commercial machine in 2006. It was quite an exciting moment as, up until that point, I’d always been on the customer side of the machine. I’d received a little bit of training and knew how many times to pull the lever on the grinder hopper to get a certain amount of ground coffee; I knew to tamp the coffee and I knew which button to press on the espresso machine. The first espressos I produced were exactly what I expected at the time: dark, strong and very intense. Being able to drink an espresso became something of a rite of passage in the coffee shop where I worked. In a sense espresso was seen as a ‘pick me up’ or a caffeine hit as opposed to a drink to savour and enjoy.
Eight years on and I’m still making espresso. Things are a little different now though. I’ve spent the intervening years learning a lot about this little beverage. I’ve read things, I’ve listened, I’ve tried things and my approach to making espresso has evolved into something a little more sophisticated. In 2006 I really had no idea what I was trying to achieve, I didn’t really know what an espresso was, and if I did manage to create a ‘perfect’ shot it was often due to luck rather than any particular skill level. Today I still chase that ‘perfect’ shot and I have a better idea of what I am trying to achieve.
In simple terms, although nothing about espresso seems that simple, when I pull an espresso shot I am aiming to achieve an extraction of somewhere between 18 and 20%. Everything I do along the way, from grinding through to the amount of water I use, contributes (or potentially takes away from) this ideal extraction.
When I think of extraction in terms of coffee, I find it easier to use the analogy of squeezing a lemon (not a totally accurate analogy but it suits my thinking). When I squeeze the juice out of a lemon, I apply a certain amount of pressure for a certain amount of time. My aim is to remove all the juice but to discard the white pith and the rind. Squeeze for too long and I risk including some of the bitter pith; on the other hand if I don’t squeeze for long enough I won’t obtain all the juice. From a lemon weighing 102g I managed to squeeze 47g of juice – 46% of the lemon ended up in my cup, the rest was thrown away.
In respect of espresso I use water to exert pressure on the coffee bed and I want to extract 18-20% of the coffee into the up. The other 80% or so is waste which will be thrown away as spent grounds. Anything less than 18% and the coffee will be under extracted, which can result in a weak, harsh and sometimes unpleasant coffee. With the lemon analogy above it is easy to see when all the juice has been squeezed out; with espresso everything happens within a portafilter, hidden somewhat from view.
Over the intervening years I have come to understand the importance of having a specific espresso recipe which helps achieve this desired extraction. As a basic starting point I use the weight of the dry grounds, the weight of the resulting espresso and the extraction time as the three parameters in my recipe. For example, I often pull an espresso to the following parameters:
18g dry grounds
29g espresso weight
30 second extraction
I am now in a fortunate position to be able to measure the extraction of my espresso using a refractometer. For those not in this position and wanting to play around with their espresso at home (or at work) I would suggest you invest in a set of scales and play around with a few recipes. You can then measure these recipes using the most reliable of tools, your taste buds! The bottom line in all of this is to produce an espresso which you enjoy drinking.