Table 1 (continued) 



Fig. 50. Block lifts ribbon. 



Possible Causes 



1. Ribbon electrified. (Check by testing 

 whether or not ribbon sticks to everything 

 else) 



2. No clearance angle (see Fig. 34) 



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 



Remedies 



1. Increase room humidity. Ionize air, either 

 with high frequency discharge or bunsen 

 flame a short distance from knife 



2. Alter knife angle to give clearance angle 



3. Scrape upper surface of block with safety- 

 razor blade 



4. Clean knife with xylene 



Defect 



1. Because wax crumbles 



2. Because sections, though individually per- 

 fect, do not adhere 



3. Because sections roll into cylinders 



No ribbon forms 



Possible Causes 



1. Wax contaminated with clearing agent 



2. Very hard, pure paraffin used 



for embedding 



3a. Wax too hard at room temperature for 

 sections of thickness required 



b. Knife angle wrong 



Remedies 



1. Reembed. {Note: Wax very readily absorbs hydrocarbon vapors) 



2. Dip block in soft wax or wax-rubber medium. Trim offsides before cutting 



3a. 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 



