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Frits come in differing standard porosities, and a full range of diameters, from tiny to 380 mm. We can provide frits of all porosities and various diameters, although stock sizes will always be less expensive. We are distributors for ROBU porous glass filters, and stock mostly their frits, so the P- series porosities are easy for us.
Fritted
filter disks are available in a range of diameters. In millimeters, they
start at 5, 10, 20, 25, 30, and up in ten mm increments to 380 mm diameter
(!). The really big diameters are really expensive (if you have to
ask, you probably can't afford them). We stock many of the smaller to medium
sizes in the most useful porosities. Custom sizes are available; please contact
us with your specifics. The thicknesses of the frits range from 2 - 3 mm
for small sizes to 8 - 10 for the larger (~150 mm); they are intended to
withstand a pressure differential of one atmosphere (i.e. vacuum).
Below are the porosity
specifications for the major manufacturers, and the pore volumes for different
porosities.
American standards
- (Kimble & Corning,
ASTM) nominal pore size, in microns
Designation |
Pore size, in microns |
Extra Coarse |
170-220 µm |
Coarse |
40-60 µm |
Medium |
10-15 µm |
Fine |
4-5.5 µm |
Very Fine |
2-2.5 µm |
Ultra Fine |
0.9-1.4 µm |
(The parenthetical designation doesn't seem to be in use much yet, although it is much more descriptive)
Designation |
Pore size, in microns |
P00 (P500) |
250-500 µm |
P0 (P250) |
160-250 µm |
P1 (P160) |
100-160 µm |
P2 (P100) |
40-100 µm |
P3 (P40) |
16-40 µm |
P4 (P16) |
10-16 µm |
P5 (P1.6) |
1.0-1.6 µm |
Ace makes their filters from fibers, rather than particles.
| Designation |
Pore size, in microns |
| A |
145-174 µm |
| B |
70-100 µm |
| C |
25-50 µm |
| D |
10-20 µm |
| E |
4-8 µm |
Each of the three systems of pore
size specification generally cover your common needs. There
are a few specialized porosities in the finer range, such as 0.5 - .75 µm,
in limited thicknesses and diameters.
Porosities of sintered
glass filters are determined dynamically: air is forced through a frit just
immersed in water until a bubble goes through. The pressure required correlates
with the pore size, according to theory: pore diameter (in microns) = 30 *
surface tension (in dynes/cm) / pressure (in mm HG). This should correlate
with the average pore size of the whole frit.
Pore volume
for various porosities
Designation |
Pore volume in % |
P00 |
~ 32% |
P0 |
~ 35 % |
P1 |
~ 40 % |
P2, Coarse |
~ 40 % |
P3 |
~ 42 % |
P4, Medium |
~ 42 % |
Fine |
~ 45 % |
P5, Ultra Fine |
~ 50 % |
These values are measured under vacuum;
at atmospheric pressure, there may be dead end pores which would be unavailable
to your liquid.
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