Semi-Automatic Espresso Machines
Semi automatic espresso machines were the result of many years of research and development after the inception of the first espresso machines in the early to mid 1800’s. However, it was Giovanni Achille Gaggia who made the leap to the semi automatics as we know them today, submitting his boiler and spring lever group designs for patent in the late 1940’s. These developments allowed for a machine that delivers water at the necessary 8-9 bars of pressure via a pump, rather than demanding the user, or barista, to control it manually.
Many of the machines that are used today are very similar in function to these early designs, requiring a certain amount of control over the grind setting of the coffee and the pressure with which this coffee is tamped down to create a properly extracted cup. (A more in depth discussion of the grind setting and tamp pressure as they relate to one another and the resulting espresso can be found in another article called Rituals of Making Espresso.) This is where the line between art and science becomes blurred in the espresso world. Because the essence of the espresso making process hinges on the ability to control these variables, the semi automatic style does require the barista to invest time into the machine and into the process. Initially, these machines were intended solely for commercial use, but as business got bigger and demand got higher, it was clear that the public wanted a machine they could use at home. The manufacturers responded with three different types of smaller home machines in addition to what are called “prosumer” espresso makers.
The smaller home espresso machines are classified by the type of portafilter they have. The portafilter is where you place the coffee before brewing. Because the grind and tamp of the coffee are so important to the espresso, the design of the portafilter makes a large difference in the output of a semi automatic machine. Commercial style portafilters are the same as those on prosumer machines, and are very dependent on the grind and tamp pressure to provide the resistance through which the water flows. On the other hand, pressurized style portafilters create the resistance themselves, causing less of a dependence on the grind fineness. The commercial portafilters also have a 58mm diameter that provides a larger surface area from which the espresso is extracted. Diameters on pressurized portafilters run from 49 to 54mm. We will return to this topic shortly.
Prosumer machines are professional style machines that are intended for consumer use. These machines are generally large, and usually contain what’s called a heat exchanger boiler, which affords you the ability to brew and froth or steam at the same time, among other features. The heat exchanger boiler functions differently from those found in smaller home machines by pulling water for brewing and steaming from different portions of the boiler. These are not a far leap from the commercial machines, and can in fact be used in a light commercial setting.
These are the basic differences between semi-automatic espresso machines. But we still haven’t covered what is truly involved in the day-to-day use of one of these machines. We have talked a bit about the fact that time and effort are involved, but what kind of time and effort? The rest of this guide will lead you through the basic processes that comprise the semi automatic espresso making experience.
The first time you use the machine, you need to prime the boiler. This is really just pulling water from the reservoir into a dry, or empty, boiler. Priming the boiler only takes a few minutes and simply requires filling the reservoir, flipping a few switches, and turning a knob. It’s a very easy process, and it makes the machine ready for future use. For smaller home machines, it is recommended to quickly prime the machine every time you turn it on to make sure that the boiler is completely full. Due to the heat exchanger boiler, this will not be necessary with the prosumer machines. Daily priming can also be accomplished by pulling a “blank shot”. This is running water through the brew group (where the water exits the machine during brewing) prior to brewing.
After it’s been primed, it’s really only a matter of turning the machine on and waiting for it to be fully heated. All of the semi automatics have a ready light or other indicator that will alert you when the machine is ready for use. Smaller home machines, like the commercial and pressurized styles we discussed before, usually take between 1 and 5 minutes to heat up. The larger prosumers can take anywhere from 10 to 20 minutes, depending on the size of the boiler and of the machine on the whole. This wait time not only heats water to the proper brewing temperature, but also the external components like the portafilter, which only improves the temperature and quality of the forthcoming espresso. You can expedite this process a little bit by pulling a blank shot, like we discussed above, with the empty portafilter attached.
The Brewing Process
Types of Input
There are two things that go into a semi automatic espresso machine: coffee and water. This may seem like a pretty obvious statement, and it is, but both of these elements come in different forms that can ultimately affect the function of your machine and the taste of the product.
There are four forms that coffee can take to be used in a semi automatic: fresh ground, pre-ground, pods, and capsules. Fresh ground and pre-ground may seem like they’re the same thing, but most definitely are not. Packaged pre-ground espresso, like Illy Fine Grind, is normally too coarse for use in a commercial style portafilter. However, they do work very well with the pressurized machines. The only preground coffee that we have found performs well in commercial portafilters is Lavazza Blu.
Using freshly ground coffee is, from a flavor standpoint, the way to go. Grinding your own whole beans gives a great aroma from start to finish and provides the freshest tasting brew possible. Having your own grinder at home also gives you quick access to adjust your grind setting, making it much easier to troubleshoot and adhere to the golden rule. We will discuss the golden rule in the “Using the Portafilter” section of this guide.
"This is where the line between art and science becomes blurred in the espresso world."
Many machines also accept pods, which are prepackaged single shots of ground espresso. The ESE (Easy Serving Espresso) system requires certified machines and pods to adhere to the same specifications, making any ESE pod compatible with any ESE machine. This has made them the most widely used and accepted form of pods. Pod filter baskets and adapters have been created for use in commercial and pressurized portafilters, but some manufacturers have also designed entire pod portafilters. Similar to the pod system is the capsule system, in that capsules are also single pre-packaged shots of espresso. Capsules come in different shapes and sizes that are unique to the manufacturer that produces them. Usually covered in aluminum or tin, capsules highly reduce water flow over coffee because they only allow one entry point for water to reach the coffee inside. Neither pods nor capsules will give you quite the quality you will get from a fresh ground coffee, but the reduced necessity for cleaning makes it a little easier to handle.
Although coffee may seem like a secondary concern when purchasing an espresso machine, it is in fact very important. The type of coffee you are planning on using should effect the ultimate decision, whether it is based on quality, cost, or convenience. More information and direction on purchasing coffee can be found in our two-part article on purchasing coffee.
Like the forms of coffee you can use, the type of water you use also affects taste and function. The most commonly used waters, tap and well water, are often found to be “hard”. Water hardness is determined by the content of minerals. The concentration of calcium and magnesium are most commonly what water hardness refers to. These minerals can build up in the boiler and tubing inside of espresso machines, eventually restricting water flow. Although you can decalcify (remove the calcium build up) the smaller home machines, it is beneficial to avoid putting hard water into an espresso maker. Putting your tap or well water through a high quality carbon filter is the best way to remove minerals that may damage the internal portions of the machine.
Reverse osmosis, or deionized, water is something we get a lot of questions about. It is not generally recommended to use this type of water because it can eventually begin to pit the metal of the boiler, no matter the material. Very similar results can be found with the use of distilled water, and the lack of minerals in both types removes some of the flavor that positively affects coffee. If you do have one of these water systems in your home, you can reduce the potential for damage and improve the flavor by pouring in one cup of water that is not deionized or distilled.
Using the Portafilter
We’ve already briefly discussed the different styles of portafilters, but it would be remiss not to recap a little here. There are two basic styles of portafilters: commercial and pressurized. The commercial style portafilters are found on all of the prosumer and commercial style machines as well as a handful of the smaller home machines. Commercial portafilters are 58mm in diameter and weigh anywhere from 1 to 2 pounds. The head of the portafilter is commonly made with chrome-plated brass. This accounts for the significant weight of these pieces and helps to provide temperature stability, producing a better shot of espresso. Due to their construction, they are a little more finicky about the grind and tamp that you use with them. For this reason, it is very helpful to have a grinder handy to adjust if need be.
The pressurized style portafilters compensate for the grind and tamp with a different design, making it much more friendly to pre-ground coffees. They either use a valve or specially designed filter basket that will not let water flow out of the portafilter until the correct amount of pressure has developed. Pressurized portafilters range from 49 to 54mm in diameter and are usually constructed of aluminum, making them much more lightweight than the commercial style.
In addition to the commercial and pressurized styles, there are pod and capsule portafilters that allow you to use single serving pre-packaged coffee if you desire. For more information on the different types of portafilters and how they work, read our article on Comparing Portafilters.
Commercial and pressurized portafilters usually come with both a single shot and double shot filter basket that you can easily switch out depending on how much espresso you want to brew. In addition to the single and double shot filter baskets, some manufacturers offer special baskets that allow you to fit more coffee into the portafilter, making your shot stronger. Changing the filter basket will also change the volume of water you will want to dispense. This pertains to what we call the golden rule, which states that when using a commercial style portafilter, a double shot of espresso is 2 to 2.5 fluid ounces of water pulled through approximately 14 grams of ground coffee in about 20 to 25 seconds. The rate at which the coffee is dispensed is directly affected by how tightly the coffee is compressed, or, the combination of grind fineness and tamp pressure. You will want to apply about 30 lbs. of even pressure to the coffee. Tamping on an uneven surface or applying more pressure to one side over another will affect the final product. Semi automatic machines generally come with a small plastic tamper. This will work, but given that its plastic it may not last very long, so we do recommend looking at some of the other tampers that we offer for consistency and longevity. This isn’t as much of an issue with the pressurized portafilters because they do not require as hard of a tamp. However, heavier tampers make it easier to apply the 30lbs of tamp pressure required for commercial style portafilters and give you the true barista experience.
After you’ve chosen your filter basket, put in the ground coffee, and tamped it down, the only thing left to do is to affix the portafilter to the machine. This is done by simply putting the portafilter up into the brew group and turning the handle counter-clockwise.
Controlling Water Flow
Although controlling the amount of water that comes through the coffee is a relatively easy thing, this portion of the brewing process has produced three different types of machines: semi and fully automatics, and lever controlled machines. Up until this point, we’ve referred to all of these machines as semi automatics, so this might breed a little confusion. As a general term, “semi automatic” is used to describe any espresso machine that has an external portafilter and uses a pump to control the pressure and speed at which water flows through the brew group. As a more specific term, it does do all of these things, but has the added amendment that the water flow starts by the barista flipping a switch and stops this way as well. These controls will either be small rocker switches or larger lever-type switches. On the contrary, a fully automatic machine has pre-programmed buttons that allow the barista to hit the button once, causing a preset volume of liquid to be dispensed. These buttons are usually reprogrammable and may need to be changed if, for instance, you begin using a different kind of beans and the shot flow timing is affected as a result (this refers again to the golden rule). Most fully automatics also come with a manual start and stop switch if you would like the additional control. The preprogrammed buttons make fully automatics perfect in busy settings where multitasking is imperative.
In order to make a tasty cappuccino or latte, you will need to froth or steam some milk and add it to your brewed espresso. Because steaming temperature is considerably higher than brewing temperature, most home machines do require a heat up time between the two functions. However, the prosumer machines have the heat exchanger boiler that we discussed earlier, which allows you to go back and forth between brewing and steaming without any wait time. For the smaller home espresso makers, it will take 20 seconds to 1 minute for the steam function to be operational.
Traditional steam wands come on most prosumer machines. There is a bit of technique involved with traditional steam wand. You normally need to do what’s called “working” the milk, by angling the frothing pitcher and circulating the milk throughout the process. The traditional wands can come with 1-4 holes on their steam tips, but consistent steam pressure the most important feature. Other machines may come with a two-position steam wand, which is placed in the down position for frothing and up for steaming, or a Panarello wand/turbo frother. Consisting of an inner wand and outer sleeve, the Panarello wand injects air into the milk, eliminating the need to “work” the milk like you do with a traditional style wand.
The desired effect is creamy froth, so many manufacturers have also developed other accessories to help meet this end. Some have created frothing sleeves or steam tips with additional holes to more easily aerate the milk. To completely bypass the learning process, some manufacturers have even developed auto-frothing systems that pull milk out of a container, froth it, and drop it directly into your cup. Frothing is a technique that takes practice and many people look for these aids to help decrease the time it may take. The technical aspect is only half the battle; the type of milk you use is also a factor in the ease and consistency of your froth. For instance, skim milk is the easiest to froth but 2% and whole milk will give you the creamiest result. More information on frothing can be found in our In Depth Look at Frothing Milk.
As you can probably imagine there is some day-to-day maintenance that needs to be completed with one of these espresso machines. After dumping, or knocking, the spent grounds from the portafilter, you will want to rinse it off using water from the brew group on the smaller home machines and from the hot water dispenser on prosumer machines. When you’re rinsing, you also want to pay special attention to the filter baskets. This is because the small holes in the filter basket can get clogged, not only blocking the flow of future espresso, but tainting its flavor as well. Coffee can also adhere to the shower screen, so you should also run some extra water through the brew group after brewing and use a group brush to remove any remaining coffee or residue on a daily basis. Prosumer and higher end home machines have a solenoid valve that dries the puck, making it easier to clean the portafilter, its baskets, and the shower screen.
Any water that doesn’t make it into a cup or is used for rinsing falls into the drip tray. You will want to empty the drip tray quite frequently, depending on the size of the tray. The frothing wand is also very important to keep clean because of its contact with milk. Just wiping it with a damp cloth after frothing and steaming should keep the outside free and clear of crusty old milk. Shooting extra steam out of the wand when you’re done frothing helps to eliminate any milk that may be stuck inside as well.
The internal portions of the machine will also need to be cleaned out. The prosumer espresso machines require a process called backflushing, which should be completed about once a week depending on the frequency of use. This will remove any remaining coffee residue from the brew group and solenoid valve, producing a better tasting cup of coffee and a better functioning machine. The smaller home machines call for decalcifying or descaling. This involves putting the decalcifying solution into a full reservoir of water and running it through the machine every three to four months depending on the frequency of use and the hardness of your water. For all types of semi automatic machines, you will want to soak your shower screen, filter baskets, portafilter, and steam wand or attachment to remove deposits and clogs from them as well. We also recommend using a group brush to scrub off anything that may still adhere to these parts.
This is a lot of information to be throwing at you all at once, but hopefully you know a lot more about semi automatics and, more importantly, whether or not they’re right for you. However, we’ve barely scratched the surface here. If you’d like to learn more about other types of machines or look closer at a few of the things we’ve covered already, take a look at the links below.
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