Blind filtering: how to keep your espresso machine in top condition

Every coffee lover knows: a good espresso starts with fresh beans, the right grind, and a precise brewing method. But even the best baristas sometimes forget a crucial part of their routine: cleaning the brewing unit with a blind filter .
It is a maintenance task that not only keeps your espresso machine clean , but also extends its lifespan and keeps your coffee tasting great.

In this guide you will discover:

• What a blind filter is and why it is so important
• How backflushing works
• What size blind filter do you need?
• How to use blind filter powder
• How to choose the right filter basket
• Subtle tips with the filter baskets and blind filters from Barista Essentials

☕ What is a blind filter?

A blind filter (also called a backflush filter or cleaning filter) is a special, sealed filter basket that fits into your portafilter. Unlike a regular filter basket, a blind filter has no holes . This prevents water from draining, and pressure builds up in the brewing unit during the flushing process.
When the pump stops, your machine's three-way valve releases pressure, allowing water and cleaning solution to flow down the drain into the drip tray. This process flushes away coffee grounds, oils, and grease that have accumulated in the internal channels and valves.

The result:

• A cleaner brewing unit
• Less chance of bitter, rancid coffee taste
• A machine that continues to run smoothly

💡 Why blind filtering is essential

1. Flavor retention

Coffee contains oils and fats that accumulate in the brewing unit, shower plate, and valves. Over time, these oils oxidize and impart a bitter, stale flavor to your espresso. Regular blind filtering removes these flavor impurities, keeping your coffee fresh and pure.

2. Hygiene

An espresso machine is warm and humid – the perfect environment for bacteria to grow. Regular backflushing prevents these unwanted guests from nesting in your machine.

3. Enjoy your machine longer

Dirt and residue in the brewing unit can damage moving parts, such as the three-way valve. This leads to leaks or expensive repairs. A blind filter keeps the internal parts clean and extends the life of your machine.

🔍 How does blind filtering work in practice?

Blind filtering – or backflushing – is simple, but requires a consistent routine. Here's the step-by-step method :

Prepare

• Make sure your machine is up to temperature.
• Place the blind filter in the filter holder.

Add powder

• Place half a teaspoon of blind filter powder (e.g. Cafetto ) into the blind filter.
• Do not use too much: 2–3 grams is enough.

Activate

• Lock the filter holder into the brewing unit.
• Start the pump, let it run for 5–10 seconds, then stop.
• You will hear a psssht sound when the three-way valve opens and discharges the water into the drip tray.

Repeat

• Do this 5 times in a row: 5–10 sec on, release pressure, repeat.

Rinse

• Rinse the blind filter and repeat the cycle 5 times without powder to remove any residue.

Group cleaning

• Brush the shower tray and edge of the brewing unit clean.
• Optional: unscrew the shower plate and clean it separately.

📏 What size blind filter do you need?

Not every blind filter fits every machine. The diameter of your portafilter determines the size.
Here's how to determine which one you need:

• 58 mm → most commonly used in professional and prosumer machines such as Rocket, ECM, La Marzocco, Bezzera.
• 54 mm → many home machines from Sage/Breville.
• 51 mm → often Ascaso, Delonghi, Solis.
• 57 mm → some Gaggia and older Breville models.

Tip: Measure the inside diameter of your filter basket or check your machine's manual.

At Barista Essentials you will find blind filters and filter baskets in various sizes, made of durable stainless steel and suitable for many brands.

🛠 Filter baskets and blind filters: the difference

Many home baristas confuse filter baskets with blind filters .

• Filter basket : has holes, allows water to pass through and is used for making coffee.
• Blind filter : has no holes and is used for cleaning/backflushing.

Barista Essentials offers both types, so you can brew and maintain your coffee with quality materials. Choose a stainless steel version for durability and heat resistance.

📅 How often should you blind filter?

• Daily : Backflush with water only (no powder) if you make multiple espressos per day.
• Weekly : backflush with powder in case of intensive use.
• Monthly : with occasional use, but clean with powder at least once a month.

✅ Summary & advice

Blind filtering isn't a luxury; it's an essential part of your coffee routine. It keeps your machine clean, your espresso delicious, and prevents costly repairs.
Invest in a good blind filter and the right cleaning powder, and follow a regular maintenance schedule.

For quality blind filters and filter baskets, visit Barista Essentials, where you'll find various sizes for both home and professional machines.

📌 Pro tip : Hang a small maintenance schedule next to your machine. This way, you'll never forget to blind filter, and every espresso stays exactly as it should be: full, round, and clean.