Foamed (Cellulose) filters are available with pore sizes from 0.2 to 8 µm.

As can be seen from the SEM image, there are no real holes (pores) in the filter structure.

Measument of "density" or "porosity" is indirect:
Accepted methods to measure (and specify) foamed filter fabric are:

Poresize (µm)

Water stream
ml/min/cm²/bar

Bubble point (bar)

0.2

25

4.2

0.8

200

1.2

5

570

0.5

8

750

0.3

Bubble point test use the fact, that liquid is trapped due to capillary forces and surface tension in the pores of a filter.

The minimum pressure neccessary to press the liquid through the pores depends on the largest poresize. This pressure is called bubble point (pressure).

Closed mesh fabric can be generated in varios ways defined by filament diameters and binding keys (Binding keys are according DIN ISO 9354).

Binding key: 30-01 07-01-03

Binding key: 20-04 04-01-01

Binding key: 20-03 03-01-01