Performance Functional Filler

Hess Pumice Products manufactures a non-crystalline silica (NCS) line of micronized, non-hazardous amorphous silica products as functional fillers and extenders for paints, coatings, caulking, rubber, and plastics.

Non-Crystalline Silica (NCS) Functional Fillers

Because crystalline silica (CS) is now classified as a carcinogenic (and a cause of silicosis), manufacturers who have traditionally relied on an abundant supply of crystalline silica for their products are facing increasing pressures in regards to environmental concerns, health issues, and workplace rules. ••• ]


Applications for the Hess Pumice Non-Crystalline Silica fillers include:

Industrial Coatings Rubber Compounds
Architectural Paints Plastics/Fiberglass Compounds
Wood Stains Silicones/Caulkings
Exterior Coatings Epoxies

Our Microfine (NCS) Pumice Products

Hess Pumice provides five Non-Crystalline Silica products developed specifically as functional fillers for the paint/coatings and rubber/plastics industries. These micronized grades are broken out below, including links to the technical data sheet for each grade.

NCS-3 linked technical data sheet Particle size average of 3 microns
NCS-5 linked technical data sheet Particle size average of 5 microns
NCS-8 linked technical data sheet Particle size average of 8 microns
NCS-10 linked technical data sheet Particle size average of 10 microns
NCS-12 linked technical data sheet Particle size average of 12 microns

Our amorphous aluminum silicate products are non-hazardous (crystalline silica free to the detectable limit of .05%), inert, near white, pH of 7.2, with unit weights (loose) ranging from approximately 1.6 kg/gallon for the finer grades up to approximately 3 kg/gallon for the coarser grades.

Our NCS products provide outstanding scrub, burnish, and stain resistance properties due to the hardness of the particles (5.8 Mohs hardness).

Availability and Packaging

The Hess Pumice NCS products are shipped world-wide with standard packaging being in 20 kg poly-lined bags, 50 lb. poly-lined paper bags, 500 kg bulk bags, and 2000 lb. bulk bags.

Properties for Coatings

Hegman results start at approximately 5 for the coarser grades. Oil absorption ranges between 30% to 40% depending on the grade. These products are also known for their outstanding durability & weathering properties, including no known instance of frosting or chalking after several years exposed to the elements. NCS grades are also used in sheen control applications.

Hegman 5 to 8
Oil Absorption % 34 to 40
Bulking Value 0.05
Moisture less than one percent

Hess NCS: Chemical Analysis & Properties

SiO2: 76.2% pH: 7.2
AI203: 13.5 Radioactivity: 0
H2O: < 1.0 Softening Point: 900° C
K2O: 1.8 Mohs: 6
Na2O: 1.6 Crystalline SiO2: None Detected
FeO: 0.1 HMIS: 0
CaO: 0.8 GE Brightness 84
MgO: 0.05
TiO2: 0.2


pumice store logo

arrow If you’d like to sample a NCS grade (or several), we have all five NCS pumice grades available to purchase in small sample quantities via our Pumice Products Store.

arrow If you’d like to run tests and trials using our pumice in your commercial product formulation or industrial process, please contact us at salesteam@hesspumice.com with your request. We look forward to answering your questions, helping you select the best grade for your process, or helping you explore the fit of pumice for your needs. PLEASE include your name, your company or organization, pertinent project details, ship-to address, and preferred contact information in the sample request email.


We know pumice. We’ll answer your questions, help determine the ideal grade for your needs, get you sample grades for testing, or help figure out the logistics for getting pumice to you—whatever’s needed.

R&D: (208) 766-4777 x111

Sales: (208) 766-4777

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