Many of the products in the DWK Life Sciences ranges of filtration glassware utilise sintered (fritted) discs manufactured from 3.3 expansion borosilicate glass. Since they are manufactured from this type of glass they are resistant to the majority of corrosive reagents, unaffected by ammonia, sulphuric acid and other solvents that are damaging to filter paper. The sintered glassware is available in six porosity classes from 0 – 5, as outlined in the table below. The pore sizes indicated, give a range of pores present within the sinter disc. Therefore, the size of particles that will be obstructed will generally be of a size at the upper end of the range.
ISO 4793 designation
Pore Index (mic.)
Coarse filtration, gas dispersion and as a support for other filter material
Coarse precipitate filtration, gas dispersion, coarse grain material filtration
Medium and crystalline precipitate filtration, medium filtration and washing of gases
Analytical work with medium precipitates
Analytical work with fine precipitates
In addition to the above detail, sinters should be treated under the same conditions as described in the general 3.3 expansion borosilicate glass thermal properties as specified.
When using new sintered glassware for the first time, we recommend a wash with hydrochloric acid followed by several rinses with distilled water to remove any residual glass dust particles from the sinter.
In order to select the correct sinter for any specific application, in addition to the porosity, it is also useful to know the flow rates of liquids and gases through the sinters. These values are given in the charts below for water and air. The data applies to 30mm diameter filter discs. The flow rates for other disc diameters can be calculated by multiplying the value read off by the conversion factor given in the table below.