Making Sections 



Table 2 (Continued) 

 Defects Appearing while Sections Are Being Cut 



157 



Defect 



Possible causes 



Remedies 



Fig. 124. Block lifts 

 ribbon. 



1. Ribbon electrified. (Check 

 by testing whether or not 

 ribbon sticks to everything 

 else) 



2. No clearance angle (see 

 Fig. 108) 



3. Upper edge of block has 

 fragments of wax on it (a 

 common result of 2 ) 



4. Edge of knife ( either front 

 or back) has fragments of 

 wax on it 



1. Increase room humidity. 

 Ionize air, either with high 

 frequency discharge or 

 bunsen flame a short dis- 

 tance from knife 



2. Alter knife angle to give 

 clearance angle 



3. Scrape upper surface of 

 block with safety-razor 

 hlade 



4. Clean knife with xylene 



No ribbon forms 



Defect 



1. Because wax crumbles 1. 



2. Because sections, though individually 2. 

 perfect, do not adhere 



3. Because sections roll into cylinders So 



Possible causes 



Wax contaminated with clearing 

 agent 



Vary hard, pure paraffin used 

 for embedding 



Wax too hard at room temperature 

 for sections of thickness required 

 b. Knife angle wrong 



1. 

 2. 

 3fl 



Remedies 



Reembed (Note: Wax very readily absorbs hydrocarbon vapors) 

 Dip block in soft wax or wax-rubber medium. Trim off sides before cutting 

 Reembed in suitable wax. If the section is cut very slowly, and the edge of the 

 section held flat with a brush, ribbons may sometimes be formed 

 b. Adjust knife angle 



