SECTION III 



GLASS WORKING 



GLASS is the commonest material in use in laboratories. 

 Apparatus of all kinds is constructed of this material, and by 

 many and various methods is it fashioned to our use. 



Roughly, we may say there are three kinds of glass used ; 

 each, of course, capable of some subdivision. 



A. Bottle glass : Fine white (flint), green or blue. 



B. Sheet glass : Window or photographic glass (crown), 

 plate glass, " patent plate." 



C. Glass rod and tubing: Lead glass, soda glass, hard 

 glass, combustion (and Jena) glass. 



Though we have so many varieties, the methods of working 

 fall mainly into two groups 



(A) Cutting, grinding, and drilling. 



(B) Bending and blowing before the blowpipe flame. 



SUB-SECTION (A) 

 CUTTING, GRINDING, AND DRILLING 



i. Cutting Glass. Window glass is used for making up 

 lantern slides, screens for various purposes, cells, covers, 

 specimen holders, etc. ; and, as it is purchased in sheet, our 

 only business with it is in the matter of cutting and shaping. 

 The glass used for photographic plates is specially selected for 

 its plane surface, though it is only of ordinary quality. Stripped 

 negatives, therefore, are a valuable source of this material. 

 Window glass is cut most satisfactorily with a diamond, though 

 few laboratories possess such an instrument. Failing this, an 



