Your basic automobile gets you back and forth to work. You know gas is pumped through the engine to get the wheels to move. This is a basic concept that we all understand vaguely to some degree as we travel hither and thither.
If we were to draw a picture, then a diagram following the gasoline through the interior of the vehicle is a good way to understand how a car works.
Slightly related note: get a load of this.. folks, it’s the “Carpuccino”.
Err, anyway…the interior of an espresso machine can seem as complicated as the interior of a car’s engine. The inside of the espresso machine has some basic components that are common in many of the machines, though.
Like the engine that powers your vehicle, the basics are the same, but the performance can vary. It all depends on the manufacturer and how the interior parts work together.
To understand the interior of the espresso machine, it’s about following the journey of the water.
Water Reservoir or Plumbing Connection
The water reservoir is a place where the water will sit and wait to be called upon for the next cup of coffee.
It’s common for smaller machines that don’t need to make hundreds of cups per day. The water can be conditioned while it’s sitting in the reservoir. For the best espresso, it starts with the right kind of water.
A reservoir requires filling to ensure there’s always water readily available. The reservoir of any machine is only so large. If it requires filling in a commercial setting, it’s often better to get a machine that can be plumbed directly into the water line.
With machines that are set up directly to the water supply, you’ll need a water softener as well as a filtration system. This is the better option for commercial enterprises that will make hundreds of coffees per day.
How Does the Water Move through the Machine?
We know how the water gets into the machine, now. It’s added manually into the reservoir of smaller machines, or the plumbing line supplies a continuous supply of water.
Once the water is in the machine, it has to move through various areas before being pushed into a cup as your favorite beverage.
The pump is vital to the operation of your espresso machine, so it’s best to give this part more than a moment’s thought.
There are two types of pumps. Each has to produce at least 130 PSI to force the water through the machine, through the grind, and out to the cup.
At one point, commercial and home coffee machine would require an operator to pull levers to get the water to move properly through the machine.
The term “pulling an espresso” came about because of the way an espresso would have to be made. With the pump, it’s all done automatically.
When asking the question, “How does an automatic espresso machine work?” The answer is: the pump.
Back to the pumps themselves, there are two choices; the vibratory pump and the rotary pump. They are both used to make a great espresso, but there are pluses and minuses for both.
In this kind of pump, you’re getting electrical currents that move a piston. There’s a magnet inside a coil that moves up and down to provide the pressure needed to move the water through.
The electrical current impacts the magnet. The magnet vibrates and moves the piston. The piston moves very rapidly. In fact, it can push at approximately 60 pushes per second.
Rotary Vein Pump
The rotary pump doesn’t work in the same way as the vibrating one. The rotary pump has a motor that spins a small disk. That spinning disk is segmented by what are called veins.
As the disk spins, the veins move to the outer section. This creates pressure that is used to move the water.
Where Does the Water Travel as It’s Heated?
Water in the Boiler
The pressure of the water isn’t all that’s needed to push it through the grind and make coffee. The water has to be heated to the proper temperature for a great espresso.
Pressurized, heated water is held in a boiler. The pump pushes the water into the boiler where it’s heated with a heating element.
There’s another part needed for heating the water, though. In a boiler, the water isn’t heated to the same temperature without a way to control the brewing temp. A Digital Temperature Control is needed to ensure all the water is the right temp.
The control could be a PID, which stands for proportional-integral-derivative. A probe sits inside the water in the boiler and consistently reads and heats the water as needed.
The Digital Temperature Control does the same thing by adjusting the water temp constantly. There are small differences, though. The PID can be adjusted by the owner while the Digital Temperature Control cannot.
Headed to the Steam Wand
This is where it can get slightly complicated. The steam wand needs steam for its milk production. Whether a cappuccino or a cafe latte is being produced, the steamed milk needs to be created with steam.
That water is a different temperature than what is sitting in the boiler because the liquid is performing two different functions. Water for steaming milk has to be steam. That makes sense. Water for your espresso has to be way below the boiling point at approximately 195 to 205 degrees F.
There are a few ways that the boiling can be accomplished without mixing the two.
Single Boiler – This boiler has a single heating element in the boiler but two thermostats. One thermostat is set for the brewing while the other is set for producing steam. The only problem with this kind of machine is that you can’t pull shots and produce steam at the same time.
Dual Boiler – A machine with a dual boiler is exactly what it sounds like. The water is pumped into two boilers. One will heat water for coffee, and the other will make steam.
Heat Exchanger – Instead of a single boiler, there’s a boiler and a heat exchanger. A separate line runs from the plumbing to the heat exchanger. The two water temperatures will never be in contact.
Thermoblock – This type of machine has a piece of metal that has a heating coil in it. The entire piece of metal is heated and water is sent to it. It’s a burst of water that instantly turns into steam.
Once the water is heated, it’ll head on to the next step.
Out of the Grouphead – E61, Saturated, and Semi-Saturated
The grouphead is where all the coffee magic happens. The heated water will meet the grind in the grouphead. It’s where the espresso will get pulled. When following the journey of water through your espresso machine, this is where the water goes next from the boiler.
These are popular types of grouphead that were patented in 1961. The entire piece is made out of brass and weighs an incredible 9 pounds all by itself. It takes about 15 minutes for the E61 to be ready to produce coffee, but it’s an easy process.
There’s a valve that allows the heated water into the grouphead. The water will move to the portafilter. There’s another valve that releases water back to the boiler, too.
The entire brass grouphead is brought to the temperature of the water that is in the boiler. This is why it takes 15 minutes for the grouphead to be ready to disperse coffee.
The groupheads are open to the water from the boiler. Essentially, it’s an extension of the boiler. The groupheads are saturated with water, which is how they got the name.
There are lines running to the grouphead, from the grouphead back to the boiler, and a line for waste that goes to a drip tray.
The line for the boiler is activated when the machine is in use. Once it’s finished, that line is closed and the waste line is opened. It’s meant to relieve back pressure.
These groupheads require trained technicians to repair and maintain. They’re common for large commercial sites.
With these type of groupheads, the entire device isn’t open to the boiler. There are the same three common lines like the other group heads, but the only part not open to the boiler is the dispersion block.
For this kind of grouphead, it’s much easier to repair and maintain than the saturated grouphead
The Portafilter – Nearly the Last Stop on Water’s Journey
The portable filter is a basket with a metal handle. The grind is placed in the basket and tamped down. This is what’s inserted into the grouphead for your espresso.
Sizes of the portafilter vary depending on the machine. The reason you need this information is because the tamper that you buy has to be the right size. Otherwise, you’ll have unevenly compressed grind.
The portafilter is locked into the grouphead and water is forced through the grind.
Into the Cup – The Ultimate Destination
The perfectly heated water has been traveling through the machine, into the grouphead, through the portafilter and grind, before finally, ending in the cup.
While it seems like an incredibly long journey, it’s one that happens very quickly. If we were to explain the journey of gas through your car, you’d wonder how the wheels every turned so quickly.
You don’t need to know the entire journey or how machines work to deliver such a yummy beverage, but it’s fun to learn exactly what’s going on behind the scenes.
It’ll also help if you’re making a buying decision for your home or business. You’ll want to know what kind of boiler is available, and what it does that might make a difference to your coffee production.