62 



The Philippine Journal of Science 



was almost as rapid. The curve shows that this system does 

 not conform to established methods of burning pottery, which 

 involve heating the ware gradually until the maximum tempera- 

 ture is reached, maintaining that temperature as nearly constant 

 as possible for some time, and then annealing by slow cooling. 



Time in minutes. 



J 00 -rt'^ 



OC. 

















1 









- • I 





^ 































r 



-^ 































Y 



si 

































/ 































/ 

















^ 















h 



/ 



















f ? 













/ 



^ 































/ 



/ 























i 











/ 

























' 1 



> 



































T 



/ 































, 



X 

































ly 



^ 































Fig. 1. Rate of burning pottery ; a, in pile of straw ; 6, in expei-imental kiln. 



The bricks burned at each place were tested for compressive 

 strength. 



Table II. — Compressive strength of test bricks. 



Burned at pottery.* 



Burned in experimental kiln.b 



Kilos per 



square 

 centime- 

 ter. 



Pounds 



per 

 square 

 inch. 



Approxi- 

 mate 



tempera- 

 ture.": 



Kilos per 

 square 

 centime- 

 ter. 



Pounds j 



per 

 square 

 inch. 







°C. 







252 



3.596 



1,010 



262 



3,885 



207 



2.959 



1,050 



260 



3.709 



203 



2,896 



1,090 



261 



3,733 



223 



3,192 



1,150 



420 



5,993 



193 



2,754 



1,190 



428 



6,118 



' All bricks were removed at end of operation. 

 '' One brick was removed when each cone fused. 

 •^ Temperatures were determined by Seger cones. 



