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GLASS FIBER FILTERS

Glass Fiber Filters are composed of pure borosilicate fibers, with or without organic resin binder.

Sterlitech and Advantec brand Glass Fiber Filters are available in a variety of nominal pore size ratings and flow rates, to suit a wide range of applications. The purity of glass filters is dictated by the presence of binder material that acts as a strengthening agent and aids in holding the fibers together. Binderless Glass Fiber Filters offer high purity and exceptional thermal/chemical resistance. Glass filters with organic resin binder have limited resistance, but offer improved wet strength and reduced potential for fiber shedding.

Due to their superior throughput compared to other fiber filters, Glass Fiber Filters are typically used in removal of sediment and coarse particulate. High flow rates enable ideal use in applications like single and multi-process removal of sediment and coarse particulate. They are also commonly utilized in pre-filtration prior to membrane filtration for food, beverage, life science, and biopharmaceutical applications.

View the Glass Fiber Filter Data Sheet or compare glass fiber grades across brands with our Brand Equivalent Table.

Glass Fiber Comparison Table

Grade Features & Applications Nominal Retention Thickness Weight (g/m²) Water Flow a Max. Op. Temp. Binder Whatman Equivalent
Sterlitech™
934 AH Standard for suspended solids content and related measurements (SM 2540D and EPA Methods 160.2). 1.5 µm 0.43 mm 64 47 550°C None 934-AH
Grade A Precipitate proteins and cell filtration, scintilliation counting, determination of airborne particulate. 1.6 µm 0.3 mm 55 12 475°C None GF/A
Grade A-E Suspended solids and air monitoring. HEPA type air filter. 1 µm 0.33 mm 60 15 475°C None -
Grade B Collection of denatured biochemical polymers. Gas filter or prefilter. 1 µm 0.65 mm 140 30 475°C None GF/B
Grade C RIA procedures and harvesting lymphocytes. 1.2 µm 0.28 mm 50 25 475°C None GF/C
Grade D Higher volume and repetitive laboratory filtering. General prefilter. 2.7 µm 0.6 mm 120 5 475°C None GF/D
Grade E Suspended particle analysis in water, cell harvesting, prefiltration and air monitoring applications. 1.5 µm 0.35 mm 70 12 475°C None -
Grade F Diluted aqaueous solutions containing strong oxidizing, acidic, or alkaline components prior to laser spectroscopy. Meets requirements for EPA Method 1311 (TCLP). 0.7 µm 0.4 mm 80 80 475°C None GF/F
TCLP Acid treated and multi-stage deionized water rinsed. Meets requirements for US EPA Method 1311. 0.7 µm 0.4 mm 80 80 475°C None GF/F
Grade TSS Designed for EPA Methods 2540C and 2540D for testing dissolved and suspended solids in water and wastewater. Excellent wet strength. HEPA type air filter.  1.5 µm 0.43 mm 64 47 475°C None -
Grade VSS Meets requirements for Standard Method 2540E, 2540C, 2540D, and EPA Method 160.2. Air pollution monitoring, high temperature flue gas and filtration of high temperature solvents. 1.5 µm 0.43 mm 64 47 550°C None -
Advantec™
DP-70 High wet strength, very high loading capacity. Dust measurement. 0.6 µm 0.52 mm 170 20 120°C Organic -
GA-55 General purpose paper, air pollution monitoring. HEPA type air filter.  0.6 µm 0.21 mm 55 23 500°C None GF/A
GA-100 General purpose paper. Filter precipitated proteins or cells. Air pollution monitoring. 1 µm 0.44 mm 110 11 500°C None -
GA-200 Thick filter. Viscous fluid filtration (sugars and gels). HEPA type air filter. 0.8 µm 0.74 mm 175 15 500°C None -
GB-100R Low trace metal content of As, Pb, and Cd. High and low volume aerosol testing for airborne dust and metal contaminants. DNA/RNA and protein precipitate filtration. HEPA type air filter. 0.6 µm 0.4 mm 95 15 500°C None EPM2000
GB-140 Compared to GB-100R: Thicker, greater wet strength, slower filtration speed. Industrial waste analysis. HEPA type air filter. 0.4 µm 0.56 mm 140 58 500°C None GF/B
GC-50 Common prefilter (for 0.45 µmm or smaller pore sizes). Scintillation counting. Suspended solids analysis of industrial water and wastewater. HEPA type air filter. 0.5 µm 0.19 mm 48 28 500°C None GF/C,
934-AH
GC-90 High wet strength. Filter for clinical screening. HEPA type air filter. 0.5 µm 0.3 mm 100 20 120°C Organic -
GD-120 High wet strength, very high loading capacity. Common prefilter (for 1.2 µm or smaller pore sizes). 0.9 µm 0.51 mm 123 14 500°C None GF/D
GF-75 Most retentive grade. Suitable for collection of IgC and other very fine protein precipitates. Clarifies chemically aggressive solutions. Meets requirements for TCLP (EPA method 1311). HEPA type air filter. 0.3 µm 0.35 mm 75 84 500°C None GF/F
GS-25 Limited dirt holding capacity, high wet strength. Common prefilter (for 0.65 µm or smaller pore sizes). HEPA type air filter. 0.6 µm 0.22 mm 70 15 120°C Organic -
QR100 (Quartz) Superior chemical resistance. Acidic gas sampling at high (>500°C) temperatures, pollution analysis. Pre-fired at 1000°C for 2 hours to reduce organic contamination. HEPA type air filter. - 0.38 mm 85 - 1000°C None QM-A
QR200 (Quartz) Superior chemical resistance, does not absorb acidic gases. Sample acidic gases at high (>500°C) temperatures, pollution analysis.HEPA type air filter. - 1 mm 200 - 1000°C Inorganic -

a The time in seconds to filter 100 mL of distilled H20 at 20°C under pressure supplied by a 10 cm water column through a 10 cm² section of filter

Frequently Asked Questions


The pores of microporous membrane filters act as small capillaries.  When hydrophilic membranes come into contact with water, capillary action associated with surface tension forces causes the water to spontaneously enter and fill the pores.  In this manner, the membranes are easily wetted and allow the bulk flow of water through the pores.  Once wetted, hydrophilic membranes will not allow the bulk flow of air or other gasses, unless they are applied at pressures greater than the membrane’s bubble point.

Hydrophilic membrane filters are typically used with water and aqueous solutions.  They can also be used with compatible non-aqueous fluids.  Hydrophilic membrane filters are typically not used for air, gas or vent filtration since the filters would block flow if inadvertently wetted, by condensation for example.

When hydrophobic membranes come into contact with water, surface tension forces act to repel the water from the pores.  Water will not enter the pores and the membranes will act as a barrier to water flow, unless the water is applied at pressures greater than the membrane’s water entry pressure.  Low surface tension fluids, such as alcohols, can spontaneously enter and fill the pores of hydrophobic membranes.  Once all the air in the pores is displaced, there are no longer any surface tension forces and water can easily enter the pores, displace the low surface tension fluid, and pass through the membrane.  The membrane will then allow bulk flow of water for as long as the pore remain water filled.  If the membrane is allowed to dry (i.e. air enters the pores), then it must be pre-wet with a low surface tension fluid again prior to use with water.

Hydrophobic membrane filters are typically used with compatible non-aqueous fluids.  They are also commonly used as air, gas, or vent filters.  Hydrophobic membrane filters are sometimes used with water or aqueous solutions; and, in these applications, they must first be prewet with a low surface tension, water miscible fluid prior to use.

Glass Fiber Filters are exhibit high operating temperatures and are particularly economical for use as a pre-filter.

The smallest available pore size rating for the glass fiber filters is 0.3µm, as featured by the Advantec Grade GF75 and Sterlitech Grade A glass fiber filters.  It is important to note that the glass fiber filters are nominally rated and it should be expected that some amount particles ≥0.3µm will pass through these filters.

To some extent, all glass fiber filters have the potential to shed some fibers.  Acrylic resin bonded glass fiber filters typically shed much lower amounts of fibers compared to binderless glass fiber filters.  The amounts of shed fibers not only depend on the grades of glass fiber media used but are also influenced by the application conditions.  Shed fibers are not typically a concern in applications where the glass fiber filters are used as a prefilters for subsequent membrane filters.

Q. What is the difference between nominal and absolute pore size ratings?

Nominal pore size ratings are provided as a general indication of filter retention.  It is understood that some quantity of particles greater than, and equal to, the nominal pore size ratings will pass through the filters into the filtrate.  Some manufactures may associate nominal pore size ratings with percentage filtration efficiencies. Nominal pore size ratings vary from manufacturer to manufacturer and, consequently, are not necessarily equivalent. Filters from different manufactures with similar nominal pore size ratings may not actually exhibit similar retention characteristics.

Absolute pore size ratings are typically based on retention studies performed using challenge suspensions of standard microorganism cultures or particles of known size. Absolute pore size ratings represent the size of the smallest microorganisms or particles completely retained during these studies. Absolute pore size ratings are almost always correlated to bubble point specifications that are used for quality control during membrane manufacturing. For the most part, absolute pore size ratings, especially those based on microbial retention, are comparable from manufacturer to manufacturer. There is more uncertainty for absolute pore size ratings based on particle retention studies, especially for pore size ratings <0.2µm, since there are no standard methods for these studies.

Regardless of pore size ratings, it is important to understand that application conditions do influence particle retention. Even filters with absolute pore size ratings can be operated in conditions that will allow unexpectedly sized particles to pass.


The acrylic (PMA) resin binder significantly improves the wet strength of the glass fiber filters. Resin bonded glass fiber filters are easier to handle and are resistant to fiber shedding. When evaluating application compatibility, it is important to consider the acrylic (PMA) resin.  

The pore size refers to the diameter of the individual pores in a membrane filter.   Pore size is typically specified in micrometers (µm).   Most membranes and filter media actually contain a distribution of pore sizes.  Nominal pore size ratings typically refer to the predominant pore size of a filtration media; pores larger and smaller than the nominal rating may be present.  Absolute pore size ratings typically refer to the largest pore size of a membrane and it is expected that all pores will be equal to or smaller than the absolute rating.

For the polycarbonate track-etch (PCTE) and polyester track-etch (PETE) membrane filters, porosity is the percent of the total surface area occupied by the pores; it typically ranges from <1% to 16%.  For the other membrane filters, porosity is the percent of the total volume occupied by the pores; it typically ranges from 40 to 80%.

Glass Fiber Filters have nominal pore size ratings.  These ratings are not necessarily consistent between different manufacturers.  Consequently, it is possible for glass fiber filters from different manufacturers to have equivalent retention characteristics while having different nominal pore size ratings.

As a result of the manufacturing process, one side of the glass fiber filters is indeed slightly rougher than the other side. This difference does not affect performance and users need not be concerned with filter orientation. The filters will exhibit similar retention and throughput regardless of which surface is facing upstream.

You can find the Sterlitech compatibility guide.  It is important to realize that application conditions, such as operating temperature, affect compatibility.  Please contact us at [email protected] if you need assistance.

The bubble point is the minimum amount of pressure required to push air bubbles through the largest pore of a wet membrane.  The bubble point is inversely proportional to the pore diameter, as the pore diameter decreases the bubble point increases and vice versa.

Retention efficiency of membrane filters can be directly measured by challenging the filters with suspensions of standard microorganism cultures or particles of known size.  Unfortunately, such efficiency testing is necessarily destructive.  However, since retention characteristics are dependent on pore size, it is possible to correlate destructive challenge testing results to non-destructive membrane bubble point tests.  In this manner, the relationship between membrane pore size and membrane bubble point is empirically determined.  Typically, a minimum bubble point can be determined and specified for a particular pore size rating.  The bubble point specification is then used for quality control during membrane manufacture.  The bubble point can also be used by the consumer as a nondestructive test to verify membrane integrity before and/or after use.    

DOP is an abbreviation for dioctyl phthalate.  Aerosol particles made with DOP have a very uniform size of 0.3µm and are used to characterize air filter retention.  For example, DOP particles are used in ASTM D2986-95a, Standard Practice for
Evaluation of Air Assay Media by the Monodisperse DOP (Dioctyl Phthalate) Smoke
Test.

Depth filters are constructed with relatively thick filtration media and typically have nominal pore size ratings >1µm. Due to their large void volume, they capture significant amounts of particulate within their pore structure.
Membrane filters are typically composed of polymers that have been chemically processed, resulting in highly porous thin films with microscopic pore structures. Membrane filters typically have absolute pore size ratings <1µm, with some exceptions. Because of their very fine pore structure, membrane filters tend to trap the majority of particles on the surface. However, smaller particles with diameters near or below the pore size rating can be captured within the membrane or pass through the membrane.

membrane filters vs separator papers

To ensure ease of use, the membrane filters as stacked in their packaging are interleafed with layers of separator paper.  In most cases, the membrane filters will be white in color except for the track-etch membranes which are colorless and translucent.  In some special cases, the membranes will be dyed dark grey to black in appearance.  In all cases, the separator paper will be a different color than the membrane and is usually not white.  Please contact us at [email protected] if you need assistance.