Unit of measurement: g/m2
Test according to DIN 53103 and ISO536:
Typically, the weight of 500 cm2 paper with sides of 200 x 250 mm is measured.
Unit of measurement: μm
Test according to ISO 534:
The thickness is determined with a precision micrometer exerting a pressure of 25 kPa on a 2 cm2 sheet.
Unit of measurement: N/15 mm width
Test according to DIN 53112 part 1:
A strip 15 mm wide and 100 mm long is subjected to a gradually increasing load.
The force exerted when the tape is split is the splitting strength, which is carried out both in the longitudinal and transverse directions of the tape.
Unit of measurement: N/cm2
Test according to DIN 53141 part 1:
A sample placed on a 10 cm2 rubber membrane is loaded with gradually increased air pressure.
The pressure measured when the paper splits is the breaking strength.
Unit of measurement: mm water column
Test: The rupture strength of a 14.5 cm2 filter is tested under a gradually increasing water column load.
Unit of measurement: %
Test according to DIN 54370: Quotient calculated from the mass of ash remaining after burning 10 g of filter paper in a platinum crucible.
Unit of measurement: s (mp)
Gurley-test (ASTM-D726):
The time during which 100 ml of water can be filtered through a 1.56 cm2 filter at a pressure equal to the pressure of a 31 mm water column.
Using the Herzberg method:
Flow time of 100 ml of distilled water at 20 °C, at a constant water column pressure of 50 mm, on a 10 cm2 filter plate.
Test according to DIN 53137:
Flow time of 14 ml of distilled water at 20 °C freely suspended on soaked filter paper folded in four, 125 mm in diameter.
Unit of measurement: l/ m2
Test according to DIN 53887:
The amount of air that the filter lets through in the event of a 2 mbar pressure difference between its two surfaces.
Unit of measurement: g/m2
Test: The relative value of the difference between the dry and wet mass of a 100 cm2 filter. Dry paper is immersed in water for 1 minute, then excess surface water is removed using FP591 filter papers.
Test: A test with iron(III) hydroxide, lead sulfate, calcium oxalate and barium sulfate, during which the ability of the filter paper to retain precipitation is examined.
Unit of measurement: μm
Test: A dry and a membrane filter moistened with a special liquid are subjected to increasing pressure in a Coulter porosity meter.
In both cases, the amount of air passed through is measured.
Unit of measurement: bar
Test according to DIN 58355 part 2 and ASTM F 316:
Membrane filters moistened with water or – in the case of a PTFE filter – with isopropanol – continuously increase pressure on the inlet side until bubbles appear on the outlet side. The bubble point correlates with the pore size, so it can be used to check the integrity of the filter.
Unit of measurement: ml/min/cm2
Test according to DIN 58355 part 1:
The time during which a certain amount of prefiltered deionized water – or ethanol in the case of a PTFE filter – passes through the membrane filter under a pressure of 0.9 bar.