Dialing in your espresso shot is the most important skill to learn for any new home barista. To “dial in” is to set up your grinder and machine to get the perfectly timed shot. As we know, a well timed shot means that the correct amount of water is flowing through the right amount of coffee grounds at the proper temperature and flow rate for optimum extraction. In short, this means you’ll get a great shot! In our last entry in this series, we took a look at dosing. For this article, we’re discussing the most important part of the dialing in process - grind size.

Why Does Grind Size Matter?

As we’ve discussed, we’re trying to arrive at the perfect combination of coffee grounds, water, temperature, and size. The reason that size is important in this equation is that size, along with dose, controls flow rate. A finer grind restricts water flow, and the proper size will result in the correct flow rate for your shot. Generally, a grind that is too fine will result in over-extraction, and a bitter shot. A grind that’s too coarse will cause a fast shot, resulting in a sour, under-extracted taste.

One of the reasons we call this process dialing in in the first place is because it involves setting the grinder size dial to the right setting. The trouble is finding that sweet spot. So how do we do it?

Finding the Grind

The reason we covered dose over grind size in our last article is because it’s a variable we can eliminate. Because the trickiest part of the process is finding the right grind size (as it varies with each bean), we want to eliminate every other variable first. A well-made espresso machine will take care of water temperature for you, and as we discussed last time, consistent dosing of coffee and water takes care of the volume piece of the puzzle. The last thing we need to determine is grind size.

For a stepped grinder with set points in its dial, we recommend starting with whatever is recommended for espresso in the user manual. For a stepless grinder, you’ll want to take the grind as fine as you can without the burrs grinding each other. Next, you’ll want to pull a shot with all of your other parameters set up properly. Check the shot time, if you pull a 2:1 ratio shot at around 25 seconds, you got it in one! If your shot time is 30 or more seconds, you should try taking the grind slightly coarser. If you get a fast shot at 20 seconds or less, you’ll need a finer grind. This process can take a few tries, so don’t get discouraged if you have a tough time at first!