Porosity

Choosing the correct porosity is key for success in working with glass filters. These frits vary in porosity according to grades that are expressed as 00, 0, 1, 2, 3, and 4. The table below shows the various fields of application for each grade of porosity. The pore size indicates the largest pore in the disc, as well as the diameter of the smallest particle retained during filtration.

FRITTED DISC APPLICATIONS
POROSITY	NOMINAL MAXIMUM PORE SIZE (µ)	EXAMPLE FIELDS OF APPLICATION
	250–550	Liquid and gas distribution
	160–250	Gas distribution Gas distribution in liquids at low pressure Filtration of very coarse precipitates
	100–160	Coarse filtration, Filtration of coarse precipitates, gas distribution in liquids Liquid distribution, coarse gas filtration Extraction apparatus for coarse grain minerals Loose filter layer substrates for gelatinous precipitates
	40–100	Preparatory fine filtration Preparatory work with crystalline precipitates Mercury filtration
	16–40	Analytical filtration Analytical work with medium-fine precipitates Preparatory work with fine precipitates Filtration in cellulose chemistry, fine gas filtration Extraction apparatus for fine-grained minerals
	10–16	Analytical fine filtration Analytical work with very fine precipitates (e.g., BaSO4, Cu2O) Preparative work with precipitates of appropriate fineness Non-return and stop valves for mercury