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New espresso machines advertise that they can generate very high pressures of up to 15 bar and some even more. Is such a high pressure necessary and good for brewing espresso? Let’s find out.
15 Bar in espresso machines refers to the pump pressure. For brewing espresso, a 8-9 bar pressure on the coffee is best. Some machines use high pressure pumps to make up for the loss of pressure from pump to group head and to work properly with pressurized filter baskets and larger than ideal grind.
There is a lot to know about making espresso and pressure. Let’s get into it.
Does Espresso Machine Pressure Matter?
Other types of coffee don’t require any pressure to brew so why does it matter how much pressure an espresso machine makes?
Espresso is not a type of coffee bean or a grind size. What makes espresso is the brewing method. To make proper espresso the water has to be pushed through a bed of finely ground coffee under high pressure. The pressure helps extract the coffee grounds faster. This is why you can brew such strong coffee with so little liquid and in such a short amount of time with an espresso machine.
The amount of water used to make espresso is very little compared to other brewing methods. You want to extract a certain amount from the coffee grounds for the taste to be balanced. Extract too much and you coffee will taste extremely bitter and hollow. Extract too little and it will taste sour. So while you use less water for espresso, you still want to extract the same amount from the coffee grounds as with other brewing methods to keep the taste balanced. But because you’re using just a little bit of water, that water has to do much more extraction work and the pressure helps with this.
Because the pressure in an espresso machine extracts the grounds so quickly and efficiently, you get a small amount of liquid that tastes very intense and has the thick, viscous texture.
Other things like the grind size and water temperature are the way they are to work together with the high pressure and make sure the extraction is perfect which results in a balanced tasting cup of espresso. A finer grind means there is more surface area on the same amount of coffee grounds which means more space for the water to interact. This speeds up extraction. The same goes for water temperature. The things you want to extract from coffee grounds extract faster the hotter the water is.
However, with all those factors including pressure, there is a sweet spot. More is not always better. Too much pressure, too fine a grind and water that’s too hot means the grounds are extracted too much which results in very harsh bitter taste notes. Going too far the other way will not extract enough and mean your coffee is sour.
That’s because the compounds in coffee that are water soluble don’t all dissolve at the same rate. The really sour compounds come out easily, the really bitter ones go last. The trick for making good coffee is finding that balance in between that brews the perfect tasting cup.
Is a 15 Bar Machine best for espresso?
Now you understand why you need the pressure, you might wonder what the best pressure is to brew espresso. If you’re looking for an espresso machine you’ve probably seen the pressure mentioned in the machine specs.
15 Bar seems to be the latest and greatest in espresso machines and since they’re advertising it so proudly, it must be good right?
15 bar is the pressure the pump can create. That doesn’t mean the espresso should be brewed at that pressure. Around 8-9 bar is considered to be ideal and brewing with higher pressures can lead to over extracted espresso that tastes very bitter.
First you should understand that what’s advertised or mentioned in the specifications of a certain espresso machine is the pressure the pump can create. In an espresso machine, the boiler heats the water and the pump moves it to the group head and creates the pressure there. The pressure at the group head where the coffee is, is the pressure that really counts. The pressure on the coffee grounds is what actually impacts the taste not the pump pressure.
If you would measure the pressure at the pump and at the same time at the group head, you would see a pressure drop. There are some losses along the way. In most machines there is a drop of about 1 bar between the pump and the group head. Also, almost all espresso machines will have an overpressure valve. This valve is set to open at a certain pressure so it doesn’t become too high.
In general around 8-9 bar of pressure at the group head is considered ideal. You do not want to brew espresso at 15 bar. The espresso brewed at 15 bar would come out way too fast and taste too bitter. It might even be bitter and watery at the same time.
1 bar is the air pressure at sea level. So if you have 9 bar of pressure at the group head, the water gets pushed through the coffee with 9 times the normal air pressure.
So an espresso machine capable of 15 bar of pressure rarely actually delivers that pressure at the group head because it would taste pretty horrible. So why do manufacturers advertise the super high pressures like it’s something good?
Why have a 15 bar Espresso machine?
So if you don’t need that much pressure, why get a machine that can create so much?
Having a high pressure pump does two things. The first reason manufacturers use high pressure pumps is because the cheaper machines just lose a lot of pressure between the pump and group head. Raising the pump pressure is easier and cheaper than reducing losses. And as said, even higher end machines lose up to a bar of pressure between pump and coffee.
Also, it’s good to have overhead, You want pressure to be consistent. Some pumps can create a certain pressure at peak but not sustain it over the duration of pulling a shot. Having a pump that can do more than required and then release the excess pressure through a valve creates a more constant pressure which results in better coffee.
Wondering if higher pressure would make faster shots? Click here to find out if you can make espresso even faster.
There is a third reason why some machines have really high pressure pumps. Manufacturers know most people use pre-ground coffee or coffee from mediocre grinders in their machines, especially in entry level to mid-range machines.
This type of coffee is unlikely to be ground to exactly the correct size. You actually need a pretty good grinder to get the best out of an espresso machine. If the coffee is ground too coarse and you apply 9 bar of pressure, the coffee will spray out of the machine because there is not enough resistance. Bigger coffee particles have bigger air gaps in between which the water can easily flow through. That has as a result that the coffee doesn’t get extracted properly and it will probably be weak and sour.
But manufacturers of espresso machines want you to be able to make decent coffee with normal pre-ground coffee so you don’t start complaining in the reviews. So to fix the problem of the wrong grind size, they add a pressurized filter basket. A normal (naked) espresso filter has many tiny holes in the bottom. This doesn’t provide any resistance. A pressurized basket has a double bottom. The bottom you see just has a single hole in it and the false bottom has a little pressure valve. This helps to create resistance so the correct pressure can be reached.
However, now you are using bigger coffee particles. That means there is less surface area so the extraction is slower. Since you always want to finish brewing espresso in about 30 seconds, there is one other way to increase extraction: Raise the pressure. That’s why 15 bar is necessary with a pressurized filter basket.
With a normal open basket, the finely ground coffee is what creates the resistance and because it’s more finely ground, you can use a pressure around 8-9 bar and have the right level of extraction.
Recommended Espresso Equipment
Besides an espresso machine, there are a few other tools that can make your espresso better. Here are my favorites:
- Espresso Machine: The Breville Barista Express (Amazon) is the sweet spot in price and quality for most casual home baristas. It comes with a built in grinder and most tools you need to brew espresso.
- Tamper: A nice tamper helps you tamp your grounds in the filter for the best result. Any correctly sized tamper can do the job but a nice heavy one just feels so much better in your hand than a plastic model. This Luxhaus one (Amazon) has a nice trick up it’s sleeve to make tamping very consistent.
- Beans: Good espresso starts with good beans. Using fresh beans is a big improvement over pre-ground coffee.
- Scales: Getting consistently good espresso means you have to know how much grounds is going into the machine and how much is coming out and how long this takes. A coffee scale is going to make your espresso much more consistent and also makes adjustments a lot easier. The Apexstone coffee scale (Amazon) is cheap and doesn’t look too sleek but is just as accurate as more expensive scales. The TimeMore scales (Amazon) look and feel a lot nicer but cost a bit more.
- Grinder: To make the best of your fresh beans, a good grinder is necessary. Espresso requires a good grinder to get the best results. The Baratza Sette 30 (Amazon) is a good espresso grinder that can also be used for other brewing methods and while not cheap, is good value for money. If you prefer hand grinders, the 1ZPresso JX-PRO is one of the best options (Amazon)
- Distribution tool: After grinding you can get some clumps in the coffee grounds. Those clumps should be broken up so the water can extract all the coffee grounds equally. Distribution tools are very simple things but this one (Amazon) is beautifully made and will look good in your kitchen.