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How Coffee Machines Work: An In-Depth Look

The coffee machine is one of the most popular appliances to have in homes today. So many people drink coffee but don’t have the time to devote to more complex ways of brewing. Thankfully, coffee machines do all the heavy lifting for us so that getting a cup of coffee is as simple as pressing a button.

Most coffee machines work with the same basic process to move water through coffee grounds and into your cup. There are some differences depending on the kind of coffee machine you have on your countertop.

We’re going to take a look at how three different kinds of coffee machines work:

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  1. Drip Coffee Machines
  2. Espresso Machines
  3. Keurig Coffee Machines

By the time you finish reading the information below, you will have a good understanding of the inner workings of your favorite little appliance. Take a look to learn more about how coffee machines go about making your much needed coffee every morning.

Drip Coffee Machines

Drip Coffee Machine with bag of coffee beans

If you have a coffee machine in your home, it’s probably a drip coffee machine. This kind of coffee machine runs water through the coffee before pouring the resulting brew into your cup. It’s a relatively simple appliance that takes all the trouble out of making coffee.

Components of a Drip Coffee Machine

A drip coffee machine is separated into two sections– the top and the bottom. If you were to take your coffee machine apart, you would probably find similar pieces to just about any other coffee machine of its type.

In the top you can find:

  • The Reservoir
  • The Hot-Water Tube
  • The Faucet
  • The Drip Area

The reservoir is the biggest component of a coffee machine. It is what holds the water you pour into your machine so that it can be transferred into the coffee. Reservoirs on coffee machines can vary by size. Some can hold more water than others but all of them are a simple bucket for holding water.

The hot-water tube is an insulated tube that runs from the bottom of the machine up to the faucet at the top. This tube is usually white and functions as a way to transfer the water from one place to another.

The faucet is basically a small showerhead over the coffee grounds that is used to spray the water carried through the hot water tube over the coffee. It ensures that all of the coffee grounds are saturated so that you get the quality cup of coffee you’re looking for.

The drip area separates the faucet from the coffee. It is a small piece of plastic with holes in it that controls the rate of the water falling onto the coffee grounds below.

In the bottom you can find:

  • The Cold-Water Tube
  • The Hot-Water Tube
  • The Heating Element
  • The One-Way Valve
  • The Power Cord Connection

The cold-water tube connects on one side to a hole at the bottom of the reservoir and on the other side to the tube within the heating element. It receives the cold water that you pour into the coffee machine and passes it along to get heated up.

The hot-water tube connects on one side to the tube within the heating element and on the other side to the hot-water tube that runs up through the machine to the faucet. It takes the water after it has been heated and sends it up to be sprayed over the coffee grounds.

The heating element is made up of two parts– a resistive heating element and a tube to carry the water. It is made from aluminum and is used to actually heat the water. It connects the cold-water tube to the hot-water tube and does all the work in between.

The one-way valve is either in the hole of the reservoir or in the tube of the heating element. It ensures that the water flowing through your coffee machine keeps moving in the right direction.

The power cord is simply what you plug into the wall to give the machine power. It’s the energy for all of this to work. You wouldn’t have any coffee without it.

How the Heating Element Works

The heating element in your coffee machine is a very important component. It serves two very important functions in the coffee-making process. It heats up the water before it is sprayed over the coffee grounds and it keeps your coffee warm after it’s made.

The resistive heating element is simply a coiled wire that heats up when it is supplied with electricity. It is usually embedded in plaster so that it will last much longer. The resistive heating element is placed between the metal warming plate that sits beneath your coffee pot and the aluminum water tube.

The aluminum water tube is how the water passes through the heating element. It is connected on either end to the cold-water and hot-water tubes and passes the water along beneath the resistive heating element so that it gets nice and hot.

Between the resistive heat element and the warming plate is a white grease that is used to help distribute the heat throughout the plate to keep your coffee warm. This grease is not easy to clean up, so be careful if you ever come in contact with it!

Controlling the heating element is done first and foremost by the power switch. When you turn the coffee machine on, it begins to supply electricity to the heating element so that it can get hot.

There are also sensors that detect when your coffee machine is getting too hot and respond accordingly. They can shut off the heating element and then turn it back on when it has cooled down. The sensors continue this cycle to keep the heating element at just the right temperature.

The Coffee Making Process

Drip Coffee Machine open with filter

Making coffee with a drip coffee maker is pretty easy from your perspective. All you have to do is fill up the reservoir, scoop in the right amount of coffee, put the pot in place, and wait. While you’re waiting, the coffee machine is working on getting everything ready for you.

Here’s a look at the journey from water to coffee through your machine:

  1. It all starts in the reservoir. You pour your cold, filtered water in and close it up to let it do its business.
  2. The water moves through the hole in the bottom of the reservoir into the cold-water tube underneath.
  3. The cold-water tube passes the water through the one-way valve into the aluminum tube beneath the resistive heating element. The water will move part of the way up the hot-water tube within the machine.
  4. When you turn the coffee machine on the heating element starts to get hot. After a few minutes, the water contained in the aluminum tube will start to boil.
  5. The boiling water creates bubbles that are big enough to push the hot water through the hot-water tube all the way up through the coffee machine to the faucet.
  6. The faucet sprays the hot water so that it can even drip over the coffee grounds.
  7. The hot water saturates the coffee grounds and carries their flavors with it down into your waiting coffee pot.

Fixing a Clogged Coffee Machine

If your coffee machine is not functioning the way it should, then it’s probably clogged. Here are a few simple steps you can take to unclog it so you can enjoy your coffee.

Clean out your coffee machine. You can add a cup of vinegar to a reservoir full of water and run your coffee machine as normal. Once all of the water has gone through the machine discard the rinse water. Run a reservoir full of clean water through your coffee machine a couple of times to get rid of the vinegar completely.

Make sure the drain hole isn’t clogged. The hole at the bottom of the reservoir is how the water gets through the machine. If it’s stopped up you should unclog it using a small wire or toothpick to let the water flow through again.

Check the water spout. Make sure the spout where the coffee comes out is completely clean and not being blocked by anything.

Clean out the valve. You will have to remove the base of the coffee machine to get to the valve. Make sure your coffee machine is unplugged before cleaning the valve with warm water and detergent. This should remove any mineral deposits blocking it.

Regularly clean your coffee machine. Keeping the machine clean will prevent clogging and keep your coffee tasting fresh and clean every single morning.

Espresso Machines

Instead of regular hot brewed coffee, some people enjoy a nice strong shot of espresso to start the morning with more of a punch. Espresso machines are handy little things that use pressure to get as much caffeine into a small portion of coffee as possible. They also have their own unique way of making coffee.

Components of an Espresso Machine

Espresso machines are typically all made up of the same essential parts to get you from water to a highly caffeinated shot of coffee. There are variations that range from extremely simple to exceedingly complex but for the machine you have on your counter; you will probably find some configuration of these components.

Parts of an Espresso Machine:

  • The Reservoir
  • The Pump
  • The Heating Chamber
  • The Steam Wand
  • The Grouphead
  • The Porta-Filter

The reservoir is where you put your water so that it can be stored until it’s time to make coffee. Any espresso machine that is used to make a couple of espresso shots at a time will have a reservoir attached. Larger machines that are used for commercial purposes are more likely to be hooked up to a water source that supplies a steady stream of water at all times.

The pump is the part of an espresso machine that applies the pressure necessary to push the water through the coffee. It takes 9 bars of pressure to achieve this and that’s where the pump comes in. Espresso machines will have one of two kinds of pumps in them.

  • A vibratory pump uses a magnet, piston, and metal coil to apply pressure. When electricity is supplied the piston moves at about 60 pushes per second to push the water through the machine. Vibratory pumps are less expensive and easier to replace.
  • A rotary pump is made up of a small motor that spins a sectioned disk. As the disk spins, it presses against the outer wall of the chamber it is set in, creating the needed pressure. Water comes in at the large section of the chamber and is pushed out as it reaches the smallest part. Rotary pumps are quieter and usually last longer.

The heating chamber is a metal container that holds the water while it is being brought to a boil. The heating element within the chamber is similar to the one in a drip coffee maker. It is made up of a resistive heating element embedded in plaster at the bottom of the heating chamber. This heating element is a coiled wire that gets hot when electricity is applied.

Most espresso machines contain a simple heating element that works on an internal thermostat. It keeps the heating element from becoming too hot but gives you no control over it. More advanced espresso machines might employ some kind of outward heating control that allows you to set the temperature yourself.

The steam wand is used in those instances when drinks such as lattes are desired to mix your espresso in. Its function is to steam and froth milk for these kinds of drinks. It is connected to the heating chamber. When a valve is turned, steam from the heating chamber is released through the steam wand into the milk, making it warm and frothy.

The group head is the mechanism in the espresso machine that carries the water from the heating chamber through the porta-filter and into your cup. This is probably behind the panel of the machine where the buttons are located.

The portafilter is a metal filter with a handle and is where the coffee grounds are placed. Finely ground coffee is put in the basket and pressed down with a tamp to compress them firmly. The portafilter is put into the machine under the group head and locked in so that it’s ready to go.

The Coffee Making Process

Espresso machines are a fast and easy way to get an intense concentration of caffeine in only a couple of ounces of coffee. Once the water is heated up you will only be waiting for about 30 seconds before your shot is ready to go.

Here’s how you get from water to espresso:

  1. You fill the reservoir with water and turn the machine on.
  2. The machine starts to heat the water in the heating chamber and lets you know when it’s at the perfect temperature.
  3. You take the portafilter out of the machine and fill it with the appropriate amount of finely ground coffee. After tamping it down you lock the portafilter back into the machine.
  4. With your coffee ready to go, you put a small cup under the spout to catch the espresso when it’s done.
  5. Turning the machine to the espresso setting will engage the switch within it that tells the machine it’s time to go.
  6. The pump will activate and begin to pressurize the water inside the heating chamber until it reaches about 220 psi of pressure.
  7. All of that pressure forces the water out of the heating element through the coffee grounds in the portafilter and out of the spout into your cup.

If you want to heat some milk to add to your espresso you will have to follow a few more steps:

  1. Fill a cup with the amount of milk you need and put it under the steam wand, submerging it in the milk.
  2. When you switch your espresso machine to steam it will activate a valve in the heating chamber which releases the steam from the boiling water through the wand and into the milk.
  3. If you hold the steam wand near the surface of the milk it will make it frothy.

Common Problems with Espresso Machines

No Espresso Comes Out
No Water Flow to the Pump
Check that the reservoir is filled with water.
Check that your water supply is functioning properly.
Check there is not too much coffee in the portafilter and that the coffee is not packed in too tightly.
If your pump is clogged, run through a descaling process to clear any mineral deposits.
Check that there is no coffee built up on the screen of the group head.
Espresso Comes out too Fast
Coffee is too Coarse Not Enough Coffee
Use coffee grounds that are fresh and finely ground.
Make sure there are enough grounds in the filter and that they are tightly tamped.
Espresso Comes Out too Slow
Pump Isn’t Working Properly
Too Much Coffee
Check to ensure the pump is producing pressure and is getting enough water flow.
Make sure not to tamp the grounds too tightly, overfill the portafilter, or that the coffee is too finely ground.
Pump is Making a Loud Noise
Not Enough Water Flow
Make sure your reservoir is filled with water.
Coffee Grounds in Your Cup
Damaged Filter Basket
Bad Group Seals
If your filter basket is dented it won’t stand up to pressure and needs to be replaced.
Clean the group seals on your filter and replace them yearly to ensure no grounds get through.

Keurig Coffee Machines

Keurig Coffee Machine with a cup of coffee

The Keurig is perhaps the most popular coffee machine currently on the market. It is a

single-serve coffee maker that uses small pre-packaged containers of coffee to brew the perfect single cup. It uses methods of both a drip coffee machine and an espresso machine to go from water to coffee.

Components of a Keurig

As all things are in this day and age, a Keurig is a bit more technically complicated than a simple coffee machine. When you take a look at the inside of the machine it is a mess of wires and tubes that have no comprehensible meaning.

The Parts of a Keurig Coffee Machine:

  • The Reservoir
  • The Pump
  • Heat Resistant Tubing
  • The Heating Element
  • 2 Needles

The reservoir is the same as a reservoir in a drip coffee machine, except more advanced. Its basic purpose is to hold the water that will be turned into coffee. You fill it up with cold water that will be transferred through the machine and through the K-cup to your mug.

Within the reservoir, there is a filter system and a water level sensor.

The filter system sits at the bottom of the reservoir and helps prevent any sediments in the water from getting into the rest of the machine. The filter in this system should be changed regularly to keep it functioning properly.

The water level sensor features a small magnetized disc that interacts with a sensor to ensure there is enough water in the reservoir for the Keurig to function without burning out. As long as the disc is floating there is enough water to go through the brewing process. If the sensor loses contact with the disc the machine will turn on the Add Water indicator light.

The pump sits alongside the filter system and draws water from the reservoir into the base of the Keurig. The water is pushed by the pump through the heat resistant tubing in the Keurig to the heating element to be warmed up.

The heating element is where the water is heated up for your coffee. It has a sophisticated system of heating water consistently regardless of how much water is in the reservoir. The water level sensor has the power to cut the electricity to the heating element in case there is not enough water. If there isn’t an appropriate amount of water then the heating coil could burn out.

Two needles located within the brewing chamber of the Keurig are used to pierce the K-cup in order to let the water through the coffee grounds. When you lift the lid of the Keurig one needle is located on top of the chamber and one needle is on the bottom. The two holes these needles pierce in the K-cup allow the water through the filter and out again.

Along with these components, there are a number of small computerized parts to a Keurig that regulate the electrical current and keep everything running smoothly within the machine.

The Coffee Making Process

Keurig Coffee Machines Reusable Pods

Using a Keurig a pretty straight forward process. You don’t even have to measure out coffee to use one. All you have to do is pop a K-cup into the coffee machine and tell it to get to work.

K-cups are made up of a small plastic cup, a foil lid, and a paper filter filled with your coffee grounds of choice. When you place a K-cup in the Keurig and close the lid, the needles pierce the lid and the bottom of the plastic cup to give the water a channel to flow through.

Here’s how a Keurig coffee machine makes your coffee:

  1. First, you turn the machine on and let it know to start heating up.
  2. The heating element heats to the ideal temperature using sensors to ensure your water never gets too hot or cold.
  3. After lifting the lid you place your K-cup in the brewing chamber and then press the handle down. You should hear a faint pop as the needles pierce the K-cup.
  4. You can choose the number of ounces you want depending on how big your coffee mug is.
  5. When you place your cup under the spout you press the button to tell the Keurig to make the coffee.
  6. Water is pushed by the pump through pressurized tubes through the heating element so that by the time it reaches the coffee it is at the perfect temperature.
  7. The hot water is pushed through the coffee grounds in the K-cup and out the bottom so that it goes through the spout and into your cup.

Common Problems with Keurig Coffee Makers

Not Working
Mineral Deposits are Blocking Water Flow
Air Bubbles
Components Aren’t Seated Properly
Make sure to use clean, filtered water that won’t leave undesired sediments behind in your machine.
Descale your machine to clean out any build-up of minerals. Fill the reservoir and give it a gentle shake while the machine is unplugged to get rid of any air bubbles.
Check to make sure all of the parts of your machine are put together correctly and seated in place.
Not Dispensing Water
Machine is Clogged
Run a cup of water through the machine to clean it out. Ensure the needles and spout are clean and free of debris.
Descale the water lines and needles to clean them off.
Not Heating Up
The Pump isn’t Working Properly
Debris Accumulated Inside the Machine
Try cleaning the reservoir to fix any ‘add water’ issues. Hold the brew button down for a few seconds to get the pump going.
You may have to get the pump repaired or replaced.
Give your machine a good cleaning to get rid of any dried coffee or other debris.
Coffee Tastes Bad
Mineral Deposits Have Built-Up in the Machine
Descale your machine to clean out any build-up.
Use clean, filtered water to prevent faster mineral build-up.

Coffee Machines Make Getting Coffee Easy

These handy machines are a god-send for many people. The first thing you might do every morning is to find your coffee machine to get a good cup of joe brewing. It just isn’t the same without that boost of caffeine.

Even though it may be easy for you to make your coffee, your machine is doing a lot of clever work in order to take the water you provide it and turn it into a nice hot cup of coffee. Now that you know how they do it, you can have an even greater appreciation for them.

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