Filter Aid


Sil-Kleer filter aids are produced by subjecting a single ingredient, perlite rock (a naturally occurring volcanic glass), to a temperature in excess of 1500 F. Combined moisture within the rock vaporizes and the molten glass forms a multicelled bubble cluster, then it is milled to form amorphous-shaped particles.


Perlite filter-aids are used as a cost-effective replacement for other filter-aids, including diatomaceous earth, silica gels, and clays. They are used as both a precoat and body feed on pressure and vacuum filters of various designs, and also as a process aid for applications on pressure leaf filters, filter presses, pressure tube, pressure belt, vacuum belt, vacuum tube, and rotary vacuum filters.


Once the perlite is expanded at an extreme temperature, the relatively coarse aggregate is then milled and classified to strict specifications for particle size. The resulting particles are highly amorphous and exhibit a packing arrangement that is ideal for cake filtration. Our exfoliation process allows for separation and removal of other non-perlite volcanic glasses, i.e. obsidian, which lack the amorphous shape of the perlite and are non-filtering resulting in a superior perlite filter-aid.


Food Fermentation

Wine, beer, penicillins, cyclins, soy sauce, pickled fruits and vegetables

Industrial Fermentation

Enzymes/amino acids, bio-based chemicals, biological products, citric acid

Industrial Filtration

Solvent recovery, waste water, cyclic crudes, dyes, pigments, disposal wells, completion fluids, inks

Process Chemicals

Sulfuric acid, inorganic and organic chemicals, chlorine, molten sulfur, gum and wood chemicals

Metal Working

Coolants and oils, plating baths, rolling mill lubricants, surface agent oils




Baghouse precoat for asphalt, cement kilns, foundries and steel mills, coke ovens

Chemical Analysis

SiO2Silicon Dioxide73%

Al2O3Aluminum Oxide17%

K20Potassium Oxide5%

Na20Sodium Oxide3%

CaOCalcium Oxide1%

Trace Elements1%

Physical Properties

Hydroscopic Moisture 0%

Surface pH 6.5-7.5

Color White

Fusion Point (°F) 2300

Fusion Point (°C) 1260

Trace Elements

Manganese < 0.3%
Sulfur < 0.2%
Titanium < 0.1%
Barium < 0.1%
Gallium < 0.05%
Boron < 0.01%
Chromium < 0.0075%
Zirconium < 0.003%
Molybdenum < 0.002%
Nickel < 0.002%
Copper < 0.0015%
Lead < 0.001%*
Arsenic < 0.001%
Chlorine < 0.0005%

All analyses are shown in elemental form even though the actual forms present are mixed glassy silicates. Free Silica may be present in small amounts, characteristic of the particular ore body.

*By Food Chemicals Codex Method

Fine/Slow Flow Medium Flow Coarse/Fast Flow Air/Gas
Typical Filtration and Physical Characteristics 27-M 25-M 23-S 21-S 19-S 17-S 15-S 23-M 17-M
Flow Rate mL 300 550 750 950 1100 1300 1700 750 1300
Cake Density (lbs/ft3) 12.0 8.0 9.0 8.5 8.0 7.0 6.0 7.0 5.0
Permeability (Darcy) .2 .5 1.0 1.5 2.0 3.0 5.0 1.0 3.0
Mean Diameter (μ) 20 - 25 30 - 35 35 - 40 45 - 50 55 - 60 60 - 65 80 - 85 40 - 45 65 - 70
Size Range (μ) 5-120 5-140 5-150 5-180 5-200 5-300 5-300 5-200 5-300

Perlite Benefits

  • Sterile
  • Inert
  • Non-hazardous
  • Inorganic fused glass that is virtually insoluble
  • No color, taste or order
  • Used in standard filter equipment
  • Various packaging options (4 ft3 bags, super sacs, bulk)
  • Increased filter cloth/screen backwashing capacity
  • Kosher Certified
  • AAFCO approved as a feed ingredient
  • Classified as having GRAS status by FDA
  • Processed/stored in facility that only produces perlite

Maximized Filtration

  • Perlite particle overlay forms billions of microscopic openings and promotes higher flux rates
  • Filter aid becomes a separation medium, thus the septum media can be sized for higher flux rates
  • By forming a porous layer on the septum, you maximize capturing solids while protecting the septum
  • With proper grade selection, you can achieve increased clarity
  • Filter downtime and maintenance cost is reduced due to the added layer of filtration

Cost Advantage

Due to the light weight, 20 to 50% density advantage, Sil-Kleer offers twice as much filtration, pound for pound, than diatomaceous earth. A Sil-Kleer filter cake density is only 7 to 12 lbs per cubic foot or a dry density range of 6 to 10 lbs per cubic foot. Sil-Kleer users can realize substantial savings in filtration operations with a better filter aid at less cost.