126 



NEW YORK STATE MUSEUM 



These results were reported by John Grant in 1880. 



MIXTURE 7 days 31 days 60 days 90 days 



1-1 briq. average Of 5 107 159 188 267 



1-1 briq. w. H2SO4 added to 

 water: average of 5 129 227 260 255 



Professor Tetmajer in 1894 reported these results. 



No. Per cent of Streagth of sand briq., 1 to 3 



plaster paris per sq. In. lbs. 



added 3 days 7 days 28 days 



f 160 240 



4 \ 1 212 298 



[ 2 167 254 



f 174 285 307 



I .5 225 305 344 



I 1 227 320 408 



5 { 1.5 230 381 399 



I 2 182 290 400 



I 2.5 184 295 390 



[. 3 115 235 360 



The results reported by Candlot in 1891 were as follows : 



SULPHATE OF LIME 



P.„_ 0% 1% 2% 3% m 



MORTAR ^^^^ lbs. lbs. lbs. Ibs. lbs. 



Neat cem bria i ^ ^^^ *^*^ ^^^ ^^^ ^^ 



iSeat cem. bnq j ^g 673 738 674 790 483 



, , o A V. ■ ( 7 223 252 263 185 126 



1 cem. to 3 sand briq | ^8 333 377 377 367 201 



Lewis considers these results remarkable as regards strength 

 and not explained. 



PROCESSES OF MANUFACTURE 



About the middle of the last century the greater part of the best 

 stucco for casts was made by the artists to secure the proper 

 temperature in burning. In this way the artist was also enabled 

 to make sure that the plaster had not lost its property of quick 

 setting through absorption of water from the atmosphere. 



Usually this calcining was done in small kettles over a domestic 

 fire, and the gypsum was powdered before being cooked. In some 

 cases the cooking was done on a metallic plate instead of a kettle. 



Frequently the gypsum was baked in the baking oven/ or, as 

 it is better known, a brick oven. In this case the rock was broken 



^Knapp. Chemical Technology. Phil. 1849. 2:400-12. 



