Hess NCS: Functional and Safe

scanning electron microscope photo of pumice dust particle

A scanning electron microscope photograph showing the frothy nature of NCS pumice, even crushed to a 10-micron size particle.

salt fog exposure text comparing Minex 10 to Hess NCS 3

Salt Fog Exposure Test (ASTM B117). 500 Hours Equivalent PVC. Direct filler pigment replacement.

industrial paint process

A Functionally Beneficial Filler

Our micro-fine NCS amorphous silica grades are composed primarily of aluminum silicate, and, in structure, is a naturally calcined volcanic glass foam consisting of highly vesicular strands permeated with tiny holes. It is this distinctive, sponge-like structure that make the Hess NCS grades true functional fillers: the non-crystalline silica particles fully integrate and mesh into the polymer networks of various coatings (see image: scanning electron microscope photograph). The result is a much more functionally useful, structurally-reinforced pigment than is possible with typical platey extenders such as mica and talc. Compared to typical extenders, the following improvements in coating properties have been demonstrated:

  • Improved corrosion resistance (see image: salt-fog exposure test)
  • Improved impact resistance
  • Improved flexibility, film integrity and overall durability
  • Improved grain cracking resistance and color retention
  • Outstanding scrub and burnish resistance due to the particle hardness (6 Mohs hardness)

Replacing Crystalline Silica

Our NCS products have a lower density and must replace CS—or any other filler—on a volume basis, rather than by weight. This results in higher bulking values and higher yields per pound of NCS product verses CS product, which provides a considerable cost savings.

Gloss and sheen control with NCS is, in general, equal to and usually better than CS products. Due to NCS particle hardness (6 Mohs), scrub and burnish resistance are outstanding. Hiding power can also be improved. Additionally, NCS products work well as a replacement for Zeospheres in coatings.

Workplace Safety and Health Issues

Hess NCS grades are classified as nuisance dust only. Silica-Group 3. Crystalline Silica (respirable) has been identified as a “group 1” carcinogen by the International Agency for Research on Cancer (IARC). OSHA therefore requires all products containing more than .1% crystalline silica to be labeled as a cancer hazard. Hess NCS products are non-hazardous, crystalline silica free to the detectable limit of .05%). Download SDS (PDF).

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. Hess NCS functional filler grades are also used in sheen-control applications.


Industrial Coatings

Architectural Paints and Stains


Rubber Compounds

Plastics/Fiberglass Compounds


Grade Sizes and Characteristics:

Hess offers five Non-Crystalline Silica (NCS) grades that range from 3 microns to 20 microns in average particle size. Download the Technical Data Sheet for all Hess Non-Crystalline Silica Grades (PDF).

characteristics of Hess NCS grades (table)

Availability and Packaging:

Hess NCS products are shipped world-wide packaged in palleted 50 lb/20 kg poly-lined paper bags, 1000 lb/450 kg bulk bags, and 2000 lb/900 kg bulk bags.

We have stocking distributors in 23 countries on every continent except Antarctica, allowing us to deliver product quickly and economically worldwide.


» Download: Technical Data Sheet: Hess Non-Crystalline Silica Grades (PDF)

» Download: Product Data Sheet: Hess Non-Crystalline Silica. Includes much of the information from this website as well as testing data tables from exposure tests, scrub resistance, oil absorption, whiteness, and other tests. (PDF)

» Download: Hess NCS Characteristics Table (PDF)

» Download: Pumice Safety Data Sheet (PDF)


Our five non-crystalline silica filler grades are available to purchase in small testing quantities online via our Pumice Store.


RESEARCH: If you’re exploring how pumice may fit your particular filler extender need and would like to run some tests—then we invite you to contact Research and Development at 208-766-4777 x111 or email rd@hesspumice.com

SALES: If you want to talk availability, grades or grade blends, logistics, costs—contact our sales team at 208-766-4777 x138 or send an email to: salesteam@hesspumice.com