338 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



This brilliant whiteness proved to be cause for the sad disillusion- 

 ment of a paint manufacturer who thought this quality in a material 

 so permanent would be a fine basis for an excellent nonfading white 

 paint. He began producing such an article with the full expectation 

 of superceding all other white paints, that the diatomite would be 

 cheaper than other white pigments, and that it would not be subject 

 to oxidation and the chemical changes ordinarily affecting and dis- 

 coloring paints. But when his material was applied to a building 

 he was much surprised to learn that it gave a colorless, glazed, and 

 varnishlike surface, transparent and with no color at all except that of 

 the original surface on which it had been spread. When the form 

 of the shells, which had been responsible for the white color, was 

 modified by filling the spaces in the shells with linseed oil of nearly 

 the same refractive property for light, and the mixture was spread 

 out thin on a surface, the light was no longer reflected but passed 

 through the transparent film. This is the same effect obtained as 

 when water or oil is spread on ground glass, or when white paper 

 is permeated with oil or paraffin, and becomes translucent. 



Though this indicates that diatomite is useless to give color to 

 paint, it should not imply that it is not a useful constituent in many 

 paints, for it gives them a filling, hardening, and binding quality of 

 value, and in many paints that would be otherwise brilliant and 

 glaring, it gives a softness of luster due to the diffusion of light 

 by the fine reflecting surfaces of the diatomite particles. To obtain 

 a material that would give this effect by the crushing and grinding 

 of sand or other quartz material would be a troublesome and costly 

 process, but to obtain it by the grinding of the already frail and 

 thin diatom shells is relatively simple and easy. Hence thfc delicacy 

 of structure aids in the production of this very useful material. 



It has also a quality of hardness and resistance in silica paints 

 used for surfacing concrete and brick in damp places such as sub- 

 ways and tunnels. 



Because of its quality of reflection and radiation of light and 

 coincidentally of heat, a lining of bricks made of diatomaceous earth 

 greatly increases the efficiency of a fireplace. Less of the heat goes 

 up the chimney and more of it is thrown out into the room; also, 

 the cheerful glow of the fire is enhanced by the background of 

 white bricks. 



No more effective material than diatomaceous earth can be found 

 for insulating the walls of one's house to keep it warm in winter 

 and cool in summer. Mixed with a binding material, such as asbestos 

 fiber, it is as convenient to handle as mineral wool and is fully as 

 efficient. 



