The blind filter without which the KB90 cannot clean itself
A filter with no holes – that sounds like a contradiction, yet it is exactly the point. Because no water can get through at the bottom, it builds up in the brew group, pushes back through the valve and takes with it whatever has built up on the shower screen and in the drain path. Without this part, a machine cannot be backflushed.
This version belongs in the KB90's Straight-In portafilter, which slides straight in from the front instead of being twisted in. We do not know of a part number for this part: it is listed neither in our service parts list nor in the catalogue we otherwise take the numbers from. We do not make one up – send us the serial number of your KB90 and we will identify the part.
Descale first, then replace
A blind filter hardly scales up itself, as it has no holes in which anything could settle. Still, the note belongs here, because the blind filter is the tool that gets limescale and coffee oils out of the group in the first place: if you backflush regularly and keep the machine descaled, you will need to replace gaskets, shower screens and valve parts far less often.
Suitable products for this are in our Machine and grinder cleaning collection; for backflushing, Puly Caff Plus is a good choice, and for limescale in the group, the Descaler for E61 and BZ groups. Only when the blind filter itself is warped and no longer sits flat is replacing it the right step.
When it is due
- The filter no longer sits flat in the portafilter but wobbles or sticks up at one edge.
- The rim is bent, dented or has burrs.
- When backflushing, water escapes at the sides instead of pressure building up.
- The filter can only be removed from the portafilter by force.
- The rubber on the blind filter is cracked or missing – we stock it separately.
At a glance
| Type |
Blind filter without holes, for backflushing |
| Location |
In the KB90's Straight-In portafilter, in place of the filter insert |
| Fits |
La Marzocco KB90 with Straight-In portafilter. Machines with a twist-in portafilter need a different blind filter. |
| Scope of delivery |
One blind filter. We stock the matching rubber and the portafilter itself as separate items. |
| Version |
Original La Marzocco, Straight-In. Diameter, height and material are not documented to us. |
| Brand |
La Marzocco |
Who it is for
For every KB90 in daily use. If you run several groups in a café, it makes sense to have one per group so that backflushing at closing time does not turn into waiting. And for everyone whose blind filter no longer sits cleanly in the portafilter after years of service.
If you do not have a KB90 but a machine with a twist-in portafilter, go for the regular blind filter.
Goes well with
From our workshop in Bern and Zurich
At our places in Bern and Zurich, backflushing runs in the evening without detergent and once a week with it – followed by one more cycle with water only, until nothing foams any more. Afterwards we do not put the blind filter away wet in the drawer but dry it off; that way the rubber lasts longer. This is our routine, not a manufacturer's specification. We pull the first espresso afterwards with the Nutty Delight or the Cozy Chocolate, and for maximum body with the Very Nutty. All our roasts are listed under Coffee beans.
Returns excluded
Service parts are excluded from exchange and return. They are procured specifically for each order and cannot be resold after installation or a test fit on the machine. So before ordering, check the model, year of manufacture and serial number of your machine – or drop us a line and we will clarify the fit together. Your rights in the case of defective goods remain unaffected.
Frequently asked questions
Does this blind filter also fit other La Marzocco machines?
It is made for the KB90's Straight-In portafilter. Machines with a twist-in portafilter need a different blind filter, which we stock separately.
What is a blind filter actually needed for?
It closes off the portafilter completely. Only then does the water build up and flush the brew group back from the inside instead of simply running straight through.
How often should I backflush?
That is up to the manufacturer, not us. Our own routine in the café is: in the evening without detergent, once a week with it.
The rubber on my blind filter is worn out – do I need a new filter?
Not necessarily. We stock the rubber on its own. As long as the filter itself is flat and has no burrs, the rubber is enough.
Can I see the part at your showroom?
Yes. Come to our showroom in Bern at Gerberngasse 44 or in Zurich at Hagenholzstrasse 50b, and we will show it to you on the machine.
Questions about the fit? Write to us at [email protected]. We deliver across Switzerland and to Liechtenstein in 2-4 working days.
