746 NEW YOKK STATE MUSEUM 



brick should be, and if possible to adopt a set of standard specifica- 

 tions, a committee was appointed by tbe IS^ational brickmakers 

 association two years ago. After a series of exhaustive tests tbeir 

 report bas recently been submitted. 



The subjects which, the committee took up for consideration were: 



1 Rattling, as a measure of toughness and wearing power 



2 Absorption, as a measure of vitrification and resistance to 

 freezing 



3 Cross-breaking, as a measure of structural perfection and 

 freedom from defects due tO' manufacture 



4 Crushing, as a farther indication of the same factor 



5 Hardness, as a confirmatory test of vitrification 



6 Specific gravity, as a guide to the density and fineness of the 

 material 



The rattler. A series of experiments made by varying the 

 charge, size of rattler, number of revolutions a minute, and time 

 of rattling showed that 



1 iKTot less than 10 fo nor more than 15^ of the volume of.the- 

 rattler need be filled with the cubic contents of the charge. 



2 It must be rattled for not less than 1000 and preferably not: 

 less than 2000 revolutions. 



3 The length of the chamber is immaterial. 



4 The diameter of the chamber must be between 26 and 30- 

 inches. 



5 The speed of revolution, between 24 and 36 revolutions a 

 minute, is immaterial if the test is terminated when the requisite 

 number of revolutions have been made. 



The use of cast iron and granite as abrasive and filling materials 

 was also tested and found to be unsatisfactory. Large bricks showed 

 less wear than small ones; normally burned, less than overbumed 

 or underburned ones. 



Absorption test. A series of tests showed that even after dry- 

 ing 48 hours at above 110° C. a brick continued to lose water, and 

 that immersed brick showed redundant gain in weight even after 



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