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Ground Calcium Carbonate Versus Feldspatic Minerals

Stephen Raper, David Skelhorn


Feldspathic minerals are much more costly than ground calcium carbonate, yet they are used in interior formulations because they are perceived to have better physical properties such as scrub and burnish. These improvements are thought to be a result of the increased hardness of the feldspathic materials. But are these improvements real? Paint formulators interviewed believed these physical property improvements were real, but no one had ever verified these perceived differences. Similarly it is generally thought that exterior durability is better using feldspathic minerals rather than calcium carbonates. This paper summarizes extensive physical and optical testing of these two types of material in several interior flat paints. It was found that most of the advantages attributed to the feldspar were in fact not borne out by the data. In general, calcium carbonate can replace feldspar with no loss and, in most cases, with an improvement in physical properties. In this study it was found that replacing the feldspathic minerals with ground calcium carbonate resulted in overall formulation cost savings but gave comparable physical and exterior durability properties.

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