What is a blind filter for an espresso machine?
A blind filter is a filter basket or cleaning insert without holes, which is used in the portafilter of compatible espresso machines.
Unlike a regular filter basket, water cannot flow through the bottom. This makes it possible to build up pressure in the brew group and perform a cleaning process called backflushing.
The blind filter is therefore not used to brew espresso.
It is a cleaning tool for the maintenance of the espresso machine's brewing system.
If you want to see more equipment for espresso, you can find it gathered under espresso equipment and barista gear.
What is a blind filter used for?
When you brew espresso, the brew head, valves, and other parts of the machine's coffee path are continuously in contact with coffee and coffee oils.
Residue can build up over time.
On espresso machines designed for it, a blind filter can be used to send water – and, according to the manufacturer's instructions, possibly a suitable cleaning agent – back through parts of the brewing system.
This process is called backflushing.
The purpose is to help remove coffee oils and coffee residue from areas that are not necessarily cleaned by regular wiping and rinsing.
What is backflushing?
Backflushing is a cleaning method for compatible espresso machines.
A blind filter or a special cleaning insert is placed in the portafilter, after which the machine's pump is activated according to the procedure prescribed by the manufacturer.
Since the blind filter has no holes, water cannot flow out as it does during regular espresso brewing.
Instead, pressure is built up, which on relevant machine designs can lead water and cleaning agent through parts of the brew group and valve system.
It is important to emphasize that not all espresso machines are designed for backflushing.
Therefore, always follow the manual for your specific espresso machine.
Can all espresso machines use a blind filter?
No.
That is one of the most important things to know.
A blind filter and backflushing should only be used on an espresso machine if the manufacturer states that the machine supports this cleaning method.
Some traditional espresso machines are designed for backflushing.
Other machines use a special cleaning disc or cleaning insert.
Some have automatic cleaning programs.
And other machines must not be cleaned this way at all.
Therefore, do not use a general internet guide as a substitute for the machine's manual.
Blind filter or regular filter basket – what is the difference?
A regular filter basket has many small holes in the bottom.
During espresso brewing, water passes through the ground coffee and through the holes into the cup.
A blind filter, on the other hand, has no holes.
Therefore, water cannot run directly through the basket.
It is precisely this feature that makes the blind filter suitable for backflushing on machines designed for it.
In short:
Regular filter basket: used to brew espresso.
Blind filter: used for cleaning and backflushing.
How do you use a blind filter?
The precise method depends on the espresso machine.
A typical backflush process can generally include:
- Installing the blind filter or the manufacturer's cleaning insert in the portafilter.
- Optionally adding a suitable espresso cleaning agent if the manufacturer's procedure requires it.
- Activating the machine's cleaning or brew cycle according to the manufacturer's instructions.
- Thoroughly rinsing the system with clean water afterward.
Do not use fixed time intervals or dosages across all machines.
The machine manufacturer's procedure and the cleaning agent's dosage instructions must be followed.
At Brændeholm Risteri, you will find cleaning and cleaning agents for espresso machines, including products intended for the removal of coffee oils and coffee residue.
Should you use cleaning agent with a blind filter?
Not necessarily every time.
It depends on the machine's maintenance procedure.
Some manufacturers describe both rinsing with clean water and periodic cleaning with a suitable cleaning agent.
Other machines have special programs and their own recommendations.
If a cleaning agent is to be used, it must be a product intended for that specific cleaning task.
A cleaning agent for coffee oils is not the same as descaler.
Cleaning and descaling are two different things
It is important not to confuse backflushing with descaling.
Backflushing and cleaning
Backflushing is used on compatible machines to help remove things such as:
- Coffee oils
- Coffee residue
- Deposits around the brew group and relevant internal coffee paths
Descaling
Descaling deals with mineral deposits from the water.
Limescale does not arise from coffee, but from minerals in the water.
Therefore, you cannot automatically use a descaler instead of a cleaning agent for backflushing – or vice versa.
See our complete selection of cleaning, descaling, and water filters for coffee machines.
What is Cafiza?
Urnex Cafiza is a cleaning agent for espresso and coffee equipment, developed to remove coffee oils and coffee residue.
Cafiza is available as cleaning powder and cleaning tablets, among other forms.
Powder can be used for backflushing on compatible traditional espresso machines following the relevant procedure.
It can also be used for cleaning compatible removable parts like portafilters and filter baskets according to the product's instructions.
At Brændeholm Risteri, we have, for example, Urnex Cafiza2 cleaning powder for espresso machines. The product is specifically described for, among other things, backflushing on compatible espresso machines.
Why does the brew group need to be cleaned?
During espresso brewing, the brew group repeatedly comes into contact with coffee.
Coffee contains natural oils, and fine coffee particles can settle on surfaces and in parts of the system.
If these residues are allowed to accumulate, they can come into contact with the coffee you brew later.
Therefore, cleaning the espresso machine is not just a matter of how the machine looks on the outside.
The parts that coffee and water pass through also matter.
How often should you use a blind filter?
There is no single correct interval for all espresso machines.
The need depends on, among other things:
- The specific machine
- How often it is used
- How many espressos are brewed
- The manufacturer's cleaning system
- Whether the machine has a cleaning indicator
A machine in a café may have a completely different cleaning requirement than a home espresso machine that is used a few times a day.
Therefore, follow the manufacturer's recommended cleaning interval rather than a general rule.
Are a blind filter and a cleaning disc the same thing?
They can have the same overall purpose, but the construction can be different.
A traditional blind filter is typically a closed metal filter basket.
On some home espresso machines, a special cleaning disc or insert is used instead, in combination with a regular filter basket.
The machine may also have an automatic cleaning program that expects this specific type of insert.
Therefore, use the solution the manufacturer prescribes for your machine.
What size blind filter should I choose?
The blind filter must fit correctly with the portafilter and filter basket size your espresso machine uses.
Espresso machines come with different diameter standards.
It is therefore not enough just to buy "a blind filter".
Always check:
- Portafilter size
- Machine model
- Manufacturer specifications
- Whether the machine actually supports backflushing
The same caution applies to other espresso equipment such as tampers and precision baskets.
If you are working more with your espresso setup, you can read our page on what barista gear is.
Should the portafilter and filter baskets also be cleaned?
Yes.
Even though the blind filter is used for cleaning the brewing system itself on compatible machines, the portafilter and regular filter baskets come into direct contact with coffee with every brew.
Coffee oils and fine particles can accumulate here as well.
After normal use, loose coffee residues can be rinsed away.
More thorough cleaning should be done according to the manufacturer's recommendations and with an agent suitable for the material.
Wooden handles, rubber, electronics, and other materials should naturally not be treated the same way as loose metal parts.
A blind filter is part of maintenance – not espresso brewing itself
It is easy to focus on the coffee grinder, tamper, WDT, and dosing when trying to make better espresso.
But maintaining the equipment is also part of a stable espresso setup.
A blind filter is a relatively simple tool, but on the right espresso machine, it can be an important part of cleaning.
The most important thing is to use it correctly and only on a machine intended for backflushing.
If you want to work further on the brewing itself, you can read our guide to better espresso.
In short: What is a blind filter?
A blind filter is a filter basket without holes used for cleaning compatible espresso machines.
It is installed in the portafilter and used for backflushing, where water and possibly a suitable cleaning agent are passed through parts of the brewing system.
The blind filter is not used to brew espresso, and not all espresso machines should be backflushed.
Therefore, always check the manual for your machine before using a blind filter.
For maintenance, you will find cleaning agents for espresso machines and coffee equipment at Brændeholm Risteri.