The Espresso Guide

Posted on August 15, 2017

Introduction

This is my guide to getting started with an espresso machine and a grinder: it’s the way that I have learned to do things, and which gives me consistent and delicious shots of espresso. I’m not an expert. I’m not a barista. I’m just a guy that likes coffee, and tinkering.

Equipment

Here’s what you’ll need:

  • An espresso machine
  • A grinder
  • Coffee beans (lots)
  • Digital scales (reasonably accurate, and precise to within 0.1 grams)
  • A timer (reasonably accurate, and precise to within 1 second)

Lots of variables

Making an espresso is essentially the process of forcing hot water through compacted coffee grinds to extract the compounds that we want. There are a surprising number of variables in this seemingly simple process; enough that a tasty espresso can sometimes appear rather elusive. Coffee beans age; humidity changes; grinders heat, cool, and wear; espresso machine temperatures vary. And those are just some of the factors local to you. Before that, the coffee beans are grown, picked, stored, roasted, packed, shipped, and so on.

So with all of those variables, we need to introduce some factors that we can control more easily. I’ll refer to these as the stable factors. They are a set of values that you can write down, and to which you can refer in future. They give you a base from which to explore. The stable factors are:

  • The weight of beans going in.
  • The weight of espresso coming out.
  • The time taken to extract or pull the espresso.
  • The water temperature.

If we keep those factors constant (or at least, relatively stable over time), then we make finding that elusive tasty espresso a bit easier. Before we go any further, let’s take a quick look at what your espresso machine and grinder do.

The espresso machine and grinder

The job of the espresso machine is to heat the water to the required temperature, maintain that temperature as consistently as possible, and to force the water through the grinds at pressures of around 9 bar.

The job of the grinder is to grind your coffee beans into smaller pieces (grinds), which are as uniform and consistently sized as possible. As a rule of thumb, the better designed and built the grinder, the better it is able to do this.

Stable factors

The first two of our stable factors (weight of beans in, weight of espresso out) can be referred to as our brew ratio. In this guide, we’re going to work with double shots, using 15 grams of beans to get 30 grams of espresso. That’s a brew ratio of 1:2. There’s nothing magical about this brew ratio, nor the weight of beans. It’s just the quantities that I have settled upon over the past few years. You will almost certainly want to tweak these values to suit your beans, equipment, and taste, but for the duration of this guide, treat them as gospel. If you really want to make single shots instead of doubles, try using 7 grams of beans to get 14 grams of espresso. Everything else should stay the same.

Our next stable factor is the time taken to extract the espresso. This is known as the extraction time, and I use 25 seconds. That’s 25 seconds between starting and stopping the extraction. Again, it’s not a magical figure—it’s just one that works for me. My espresso machine does not have a built-in timer, so I use a cheap digital kitchen timer instead.

Lastly, let’s set the temperature at 92°C. My espresso machine has a PID controller: a fancy gadget that keeps the water temperature reasonably constant. I have no experience with machines that do not have one of these, so you might have to do some research if you have such a beast.

So we’ve got:

  • 15 grams of beans going in.
  • 25 seconds of extraction time.
  • Water at 92°C.

From that, we want to get 30 grams of espresso. We do that by impeding the flow of water through the coffee grinds to a greater or lesser extent. The finer (smaller) your coffee grinds, the more they will compact together, and the less space there will be through which the water can flow. The more coarse (large) the grinds, the less well they compact together, and the more space there will be through which the water can flow. We want the water to spend long enough in the grinds to extract just the right range of flavour compounds. If it spends too long in there, we’ll get too many of the compounds that spoil the flavour. If it spends too little time in there, we won’t get enough compounds.

Getting the right grind size can be tricky, especially at first with new equipment. You might be lucky and home in on the right setting within a few tries, or you might end up using a lot of beans. But once you have found the setting, you should only need to make very minor adjustments to accommodate most beans and tastes.

The process

The process is simple:

  1. Grind some beans.
  2. Tamp the grinds into the portafilter basket.
  3. Pull and weigh an espresso shot.
  4. Weigh, adjust, repeat.

Let’s go through each step:

Grind some beans

Grind enough beans to give you 15 grams of grinds. How you choose to do that is entirely up to you. My grinder has a timer on it which can be adjusted such that the grinder stops after a preset time. This works quite well, but it is worth pointing out that it is not a particularly precise way to “weigh” your grinds. I tend to recalibrate mine about once per week. Also, be aware that as you experiment, your grinder will heat up, and its grind will likely change. You might spend an hour or two fine tuning things, only to find that the next morning, when the grinder has cooled, that it produces a different grind. It might therefore take a few days to fine tune your measurements.

Another thing to watch out for is that a surprising amount of grinds tend to stay inside your grinder. This means that each time you grind, the first few grams might be grinds left over from your previous brew. This is particularly important to remember when you are trying to adjust your grinder, as you can easily end up with two different grind sizes in a single brew, and that will really throw off your experiments. Be sure to purge any previous grinds after each adjustment. And you might also want to purge any previous grinds if they have been sat in there for a while, such as before your first brew of the day.

My grinder had a small plastic guide inside the outlet shoot. I think the idea was that it would guide the grinds into the portafilter basket. It did a reasonable job at this, but it also caused a lot of blockages. I removed it, but that does mean that the grinds spray out in all directions. So instead of grinding straight into the portafilter basket, I grind into a small metal cup, and then transfer the grinds into the portafilter basket using a teaspoon. It’s a slow process, but I’m in no hurry.

Tamp the grinds

If you spend any time reading online articles about tamping, you might get the impression that it is a very complicated process that takes years to master. But it’s not really all that hard. Transfer the grinds into your portafilter basket, and tap the portafilter a few times onto your work surface (or better, onto a tamping mat to save damaging your work surface). This will help to remove any large voids between the grains. Using a sturdy tamper, tamp down on the grinds with a force of about 30 pounds. Like most other numbers, there’s nothing magical about this one. It’s simply a recognised force to aim for. Given that the diameter of portafilter baskets varies, the actual pressure applied to the grinds is going to vary. What really matters is consistency from shot to shot. Find a force that you are comfortable with, and stick to it.

The surface of the grinds should be smooth and level. Clean the rim of the portafilter to remove any stray grinds, and put it in your espresso machine. Make sure it is seated properly.

One thing that I find useful is a naked portafilter. It’s a portafilter without a bottom or a spout. If you look at it from underneath, you see the underside of the basket. If you have not tamped your grinds properly, you’ll probably find that little jets of water spray out in random directions from the bottom of your basket. Being able to see these is a great help, because you can tell straight away if something is wrong. When you’ve got it right, you should see drips of espresso forming on the underside of the basket. After a few seconds, they should coalesce into a single stream, somewhere close to the centre of the basket.

Pull an espresso shot

Get your timer ready. Put a container under the portafilter, on top of your digital scales (be sure to zero the scales). Pull the lever (or press the button) to start the machine, and at the same time, start your timer. Turn it off after 25 seconds.

Weigh, adjust, repeat

Check the weight of the espresso. If you have more than 30 grams, then the grind is too coarse: water has been able to flow too easily between the grinds; make the grind more fine. If you have less than 30 grams, then the grind is too fine: the flow of water has been impeded too much by the grinds; make the grind more coarse. If you have no espresso at all, then your grind is quite possibly far too fine, making it impossible for the water to pass through the grinds. If that’s the case, you’ll need to make a reasonably large adjustment.

Repeat the process until you get 30 grams of espresso. You now have some stable factors from which to work. It may well be that the values given here do not produce the espresso that you were hoping for. But at least you’ve got something to work from. If you do need to tweak things, tweak only one thing at a time, then see what effect it has.