When it comes to espresso, it’s important to keep track of what we’ve done so we can see what works, what doesn’t, and what changes we should make from shot to shot. To do this we need to measure three variables:
Dose – the amount of dry ground coffee used
Yield – the amount of liquid beverage
Time – the amount of time it took to pull a shot from the second we start the shot to the second we stop it.
Each one of these variables controls a certain aspect of how a shot tastes, but for now it’s enough to know that we need to measure them.
Measure weight, not volume
For dose and yield we’re going to measure by weight so we’ll need to use a scale accurate to 0.1g. Traditionally dose was measured by either trusting your grinder, or just by eyeballing it, but if you actually weigh a few doses you’ll quickly realise that your grinder isn’t very accurate. It might spit out 18g for the first dose and then 19g for the next, and because we’re dealing with such small amounts of coffee and water in espresso, tiny variations in either can have greatly amplified effects in the finished product. After all, 1g in an 18g dose is about 5.5% of the overall weight. If you put 5.5% too much salt in a bread dough, or 5.5% too much flour in a cake batter, you’d probably notice it in the finished product. Coffee is no different.
Yield was traditionally measured by volume, but lots and lots of different things can affect how much volume a particular shot occupies. For example, 36g of a certain espresso might be 1.5oz in volume, but two weeks later that same 36g might only be 1oz. The volume difference can be explained by the fact that fresher coffee usually produces more crema - the thick, reddish brown foam that floats on top of the espresso - so volume isn’t exactly an accurate measurement of how much liquid espresso we have. 36g however will always be 36g whether it’s one week after roast or two months after roast.
Time is measured in seconds using a timer. Most of the time this is either a digital kitchen timer, one that is built in to the espresso machine, or the barista’s mobile. We measure time from the second we start to pump to the second we stop the pump, not from when we see the first drops of espresso or something similar. Button press to button press is the most accurate and easily repeatable measurement, and it will tell us exactly what we need to know.
Aside from these three variables, there are many other things that might change how an espresso tastes – water pressure, water chemistry, temperature, tamp pressure…the list goes on. The important thing for this method of making espresso is that we are trying to remove all these variables from the equation, so we’re left with only three – dose, yield and time. Through tracking these three “recipe variables”, eliminating all the others and careful, focused tasting techniques, we can create an espresso recipe that will give us excellent results every time. Consistency here is key.
Next time we’ll talk about how to eliminate non-recipe variables using good equipment and good technique.