As I excitedly awaited delivery of my new espresso machine and coffee grinder, I immersed myself in YouTube videos to learn how to make espresso and its many nuances. I was surprised how it was more involved than I expected.
Undoubtedly, the best source of good information and well made videos was James Hoffmann.
My delivery arrived. I unpacked and set up the machine and grinder on my kitchen counter. The machine was very heavy weighing a reported 55 lbs. The coffee grinder was also very heavy (12 lbs) due to its diecast construction, and it was certainly built to last.
Water quality can be an issue with espresso machines. Hard water containing high levels of soluble minerals can cause excessive scale buildup inside the machine, but pure water without any mineral content can impact the taste of the coffee. The Specialty Coffee Brewers Association of America recommends total dissolved solids (TDS) in the range 75 – 250 mg/l. A TDS meter was included in the starter kit I received with my machine, and my tap water measured 115 mg/l. I figured this was good to use out of the tap and I didn’t need to use a water filter or bottled water. Incidentally, I also measured the TDS content of water from my refrigerator after fitting a new water filter, and the TDS levels measured about the same as the tap water.
I filled the Izzo’s 3 liter water tank, switched it on, heard the pump run to fill the boiler with water and waited for it to heat up.
The boiler temperature was preset at 252°F, as was displayed on the control panel on the front of the machine.
With a heat exchanger espresso machine such as this, the temperature of the boiler is set to boil the water and produce steam, which is then used to steam milk or provide boiling water to make tea. However, if this boiling water were used to make espresso, the coffee would be over extracted which would lead to bitter and burnt tasting coffee. Heat exchanger machines have a second circuit for the brew water. This circuit passes through the boiler and the water in the boiler heats the brew water through a heat exchanger. The brew water circuit feeds the brewing group (an E61 group in the case of my Izzo Vivi – which is the most common brewing group found in prosumer semi-automatic espresso machines).
As the water cools at the brew head, its density increases and this cooler water falls downwards in the circuit returning to the inlet of the boiler. This sets up a thermal syphon whereby water circulates through the brew head keeping it warm.
Due to heat losses in the heat exchanger circuit and at the brew head, the temperature of the water that reaches the coffee for extraction (brew temperature), is much lower than the boiler temperature – typically around 50°F lower than the boiler temperature.
It’s difficult to measure brew temperature directly. A device called a scace allows brew temperature to be measured, but these devices are expensive and are used to set up an espresso machine, not to make coffee.
My machine came with a brew head thermometer installed. This provides a means to measure water temperature close to where the water meets the coffee grinds, and while the temperature measured here can still be around 7°F higher than at the coffee, it provides a better estimate of brew temperature than merely assuming the temperature will be 50°F lower than the boiler temperature.
Boiler temperature can be adjusted, and providing the temperature exceeds the boiling point of water at the pressure in the boiler, steam will be produced. The higher the temperature, the higher the steam pressure. Changing the boiler temperature also changes the brew water temperature, this allows brew temperature to be optimized to achieve the required coffee extraction while still providing steam in the boiler. The PID controls the boiler temperature to maintain the desired temperature.
Switching my machine on from cold, the boiler reaches its setpoint temperature (currently set at 252°F) in around 10-15 minutes, but it takes up to 40 minutes for the brew head to reach a stabilized temperature (typically around 210°F measured by the brew head thermometer on my machine).
Initially, I saw this as a drawback of using an espresso machine. I was used to switching my Keurig machine on in the morning and having a coffee 2 minutes later. Also I could program the Keurig to switch on and be ready to brew in the morning, there are no such timers on these traditional semi-automatic espresso machines. I wasn’t prepared to wait 40 minutes for my morning coffee. I got round this by using a Wyze smart plug that I have set to switch the machine on at 5:00 am and off again at 6:30 pm. All I have to do then is to make sure there’s sufficient water in the water tank.
There are two pressure gauges on the front of my Izzo Vivi.
The gauge on the left shows the boiler pressure, which is a function of boiler temperature. The gauge on the right displays the brewing pressure during espresso extraction. This should be around 9 bar, and it was set correctly as received. I’d seen reviews of other machines where the brewing pressure needed to be adjusted on new machines, which in some cases involved removal of the casing to gain access to an adjustable pressure relief valve. I was pleased I was saved this trouble.
Onto making coffee.
A portafilter houses a basket which is filled with ground coffee. Ground coffee is evenly distributed across the basket and compressed (tamped) with a tamper forming a ‘puck’ of densely packed coffee. The portafilter is then fitted to the machine, a lever actuates valves in the brewing group which directs the flow of hot water through the coffee. The water flows under pressure created by the machine’s pump and resistance created by the small holes in the basket and the densely packed coffee. Features in the brewing group promote an even flow of water across the entire area of the coffee puck. The goal is to achieve even flow across all the coffee to evenly extract the flavor from the coffee.
Water will take the path of least resistance through the puck, so it will form channels through less dense regions of the puck leading to under extraction. To achieve even extraction the grinder should produce consistently sized grounds which should then be evenly distributed throughout the basket and tamped evenly.
My Izzo machine was supplied with two 58 mm (standard size) portafilters, one for a single shot with a single spout and small basket and one for double shots with twin spouts and a larger basket.
Espresso is commonly made with a double shot portafilter, the single shot portafilters are rarely used and single shot espresso is more difficult to make well consistently. The starting point is to grind, distribute and tamp 18 g of coffee in the portafilter. From there, the brew ratio (weight of the liquid coffee produced : weight of the ground coffee) can be altered depending on the desired strength and mouth feel (a lower ratio will produce a smaller quantity of coffee that tastes stronger and is more viscous). A brew ratio of 2:1 is often recommended as a starting point so 18 g of ground coffee would yield 36 g of liquid coffee.
Extraction time, which is measured as the time period from initial actuation of the brewing group and pump by throwing the lever, to the time when the desired mass of coffee has been extracted, should typically be in the 25 – 35 seconds range. This extraction time is achieved by adjusting the grind. If it takes less than 25 seconds to extract 36 g from 18 g of ground coffee then the coffee is ground too coarse which reduces the resistance to the water flow. This results in under extracted coffee, which can taste sour, salty and will lack sweetness. On the other hand, if it takes longer than 35 seconds then the grind is too fine and this results in over extracted coffee which can taste bitter, astringent and hollow/empty. Somewhere between the two the coffee should exhibit sweetness and taste fresh with complex acidity and have a long finish. Between the guideline 25 – 35 seconds, brew time and grind setting may be down to personal preference and taste for the coffee being used. Brew temperature can also impact the flavor profile but providing brew temperature is between 195 – 205°F it will have less of an impact on the flavor profile than the grind, puck preparation and brew time, and is normally the last variable to be adjusted, if it needs adjustment at all.
Different coffees will require different grind size depending largely on the density of the beans, and density will change based on whether it’s a light or a dark roast, the altitude the beans are grown at, and the process that’s used to roast the beans. So when switching to an entirely new coffee, it will take time a trial and error to dial-in the grind to achieve an ideal brew time. This is much easier with a fixed mass (18 g) of ground coffee and brew ratio (2:1) to reduce the number of variables.
So armed with the theory, it was time to put this into practice with my own machine.
It is accepted that the coffee grinder can have more of an impact on the quality of the coffee than the espresso machine. A grinder needs to be able to deliver coffee ground to the right grind size and the size of the particles should be consistent. The grinder I bought was an Macap M2D, which was recommended over other grinders I had been considering.
This is a burr grinder that uses 50mm flat burrs. With this kind of grinder, the coffee beans are crushed and cut between two rotating parallel burrs. Grind adjustment is achieved by moving the burrs closer together or further apart to alter the gap between them.
The particular model I have is an on demand type, meaning that it will grind as long as switch is depressed while the portafilter or dosing cup is held under the outlet. There’s an adjustable timer that can be set to achieve the required dose, but I haven’t found this to be useful as I weigh just the quantity of beans I need for each espresso I make and grind until all the beans have been ground and there is no more ground coffee coming out of the grinder. One notable feature is that this grinder has a worm drive microadjustment, which provides stepless fine adjustment of the grind size.
I’ve mentioned an 18 g coffee dose and 2:1 ratio several times, to achieve this and to be consistent, accurate measurement of weight is important when making espresso. As such, there are numerous scales available specifically designed for coffee making. The scale I bought was a TIMEMORE Black Mirror Basic Plus coffee scale. It measures to a resolution of 0.1 g and is low profile enough to fit under the brew head with an espresso or latte cup. It charges with a USB-C cable, but a charge seems to last several months.
To make a coffee, I start by weighing 18 g of beans which I then load into the hopper of the grinder. I grind until all the beans have been ground and load into the portafilter.
Initially I was grinding straight into the portafilter, but I found that ground coffee would spill out, both reducing the coffee dose and creating a mess on the counter. To counter this, I bought a portafilter dosing funnel.
This sits on the portafilter as shown, and helps prevent ground coffee from spilling out when coffee is ground directly into the portafilter. This reduced the mess, but I found I would still spill ground coffee when I removed the funnel and went to distribute the mound of coffee.
I’m currently using a dosing cup. I grind into the cup and then empty the cup into the portafilter. This seems to work well.
After distributing the ground coffee in the portafilter, I tamp with the portafilter on a tamping mat. The amount of pressure isn’t as important as ensuring consistant tamping pressure from shot to shot. The more pressure used to tamp the coffee the denser the coffee puck and the longer the brew time, therefore varying the pressure will introduce inconsistency in the quality or flavor of the coffee shot to shot.
When a heat exchanger espresso machine is left idle for some time, the water that circulates around the heat exchanger circuit with the thermal syphon becomes superheated, approaching the same temperature as the boiler. This water is too hot to make good coffee. To deal with this, it’s necessary to perform a ‘cooling flush’ to flush out all of the superheated water and replace it with water at the correct temperature. I do this without the portafilter fitted. When the valve is first opened and water begins to flow, the water will sputter accompanied by a hissing sound. This indicates that the water is flash boiling. Eventually the sputtering and hissing will stop and there will be a uniform water flow. At this point the water should be allowed to run for a further 5-6 seconds to reduce the temperature to what should then be the ideal brew temperature. This should be done every time the machine is left to idle for longer than 5 minutes, and even if left for less than 5 minutes a shorter cooling flush should be performed.
At this point we’re ready to ‘pull a shot’ of espresso, as it’s termed. To do this, I install the loaded portafilter in the machine, set the coffee scale on the grid of the drip tray and place a cup on the scale underneath the portafilter spouts.
After switching on and taring the scale, I pull the lever to start the extraction. One nice feature of my Izzo Vivi is that it has a built in automatic shot timer that starts as soon as the lever is pulled. It typically takes 6-8 seconds of the pump running before coffee starts to flow out of the portafilter, and I watch the scale and stop the extraction when I reach 36 g. At this point I look at the timer to see how long the extraction has taken. If the extraction took less than 25 seconds or longer than 35 seconds, I’d pour away the coffee and remake it with the grind setting adjusted to give me a brew time of between 25 – 35 seconds. If it took too long I’d change to a coarser grind and if the brew time was too short, I’d change to a finer setting.
When the lever is returned to the off position at the end of an extraction, then water is released from the bottom of the brewing group and into the drip tray. This is to release the water pressure. Some of this water typically puddles on the coffee scale, so it isn’t possible to stop the extraction and observe the final weight of the coffee yield. The weighing process at the end extraction is very dynamic, the weight is increasing steadily and quickly, and then increases sharply when the lever is returned to the off position and the water is dumped out of the groupset. The shot timer on the other hand, displays the total time for a few seconds before reverting back to displaying boiler temperature.
The result should be a cup of espresso covered in a 1 to 2 mm thick golden to reddish-brown layer of foam on top. This is referred to as crema, which is the result of a combination of coffee bean oils, carbon dioxide, and tiny coffee grounds that form as the espresso is brewed under high pressure.
Espresso naturally separates into different layers during brewing, with the crema on top, the body in the middle, and the heavier components settling at the bottom. Stirring helps to integrate these layers, ensuring that each sip is uniformly flavored.
A well-made espresso should offer a complex and robust flavor profile that is both intense and balanced.
A good espresso should have a rich, deep coffee flavor. The taste should be potent and full-bodied, often described as creamy or thick compared to regular coffee due to the concentrated nature of espresso.
While espresso is characteristically bitter due to the concentration of flavors and the extraction process, a well-made espresso will also have a noticeable sweetness. This sweetness comes from the natural sugars in the coffee beans that are caramelized during roasting.
A good espresso should have a pleasant acidity that brightens the flavor, rather than overwhelming it. This acidity is often described as crisp and can have a slight fruity or winey characteristic, depending on the coffee beans used.
Depending on the coffee blend and roast, espresso may exhibit notes of chocolate, nuts, caramel, fruits, or spices. These flavors should be discernible but well integrated, creating a layered tasting experience that evolve with each sip.
The aftertaste, or finish, of an espresso should be pleasant and lingering. It should continue the flavors of the drink without turning overly bitter or sour, encouraging another sip.
The crema should add a slightly sweet and slightly savory flavor that enhances the overall cup. It should be aromatic, adding to the complexity of the espresso’s taste.
Enjoy…
