GYPSUM DEPOSITS OF NEW YORK 1 3 



paints and has been found in food stuffs. Its more legitimate uses. 

 are in the preparation of insecticides and pharmaceutical supplies. 



A peculiar use of gypsum is found in the wine-growing districts 

 of Spain and Greece, where it is said to be added to red wines to 

 hasten their ripening before bottling and to give them a more fiery 

 color.^ The process is called " plastering." The gypsum unites 

 with the tartar or argol to form tartrate of lime which precipitates 

 and clears the wine, while the soluble potassium sulfate that is 

 formed reacts upon the phosphates releasing phosphoric acid which 

 enhances the color intensity. 



The presence of small amounts of gypsum in waters used for 

 brewing is said to be advantageous. 



Various processes have been devised for hardening blocks of 

 crude gypsum so as to imitate marble and other materials. The 

 blocks after being dehydrated by heat so as to render them porous 

 are treated with chemicals such as ammonia, ammonium sulfate, 

 copperas etc. A cheap substitute for meerschaum is made in this 

 way with the use of stearic acid or paraffin.^ 



Uses of calcined gypsum 



Molding and casting. The ordinary calcined gypsum, or plaster 

 of paris, has a great number of uses. A very familiar one is 9.S a 

 material for making casts and molds. The value in casting objects 

 is due largely to its property of swelling slightly as it sets, thus 

 filling out the mold perfectly. The pottery industry consumes 

 large quantities of plaster of paris annually in the form of molds 

 for casting china and porcelain wares ; the porous nature of such 

 molds is an important advantage, permitting the water of the clay 

 to escape. 



The manufacture of plate glass likewise calls for large quantities 

 of plaster. The glass sheets are imbedded in the plaster during the 

 process of grinding and polishing. It is estimated that over 40,000 

 tons are consumed each year in the United States by the glass 

 industry. 



Building and construction. Stucco and staff* are but other 

 names for plaster of paris; the former in its application to interior 

 decorations and as a white coating for wall surfaces and the latter 

 to building construction and exterior decorations. 



A related use of plaster of paris, first introduced in Germany but 

 of rapidly growing importance in this country, is in the manufac- 



' Scientific American Sup. 1907. 63:26033. 

 2 Mich. Geol. Sur. An. Rep't. 1904. 9:206. 



