58 



THE ART OF MAKING MICROSCOPE SLIDES 



Finishing 



Fig. 24. Applying coverslip to balsam wholemount. 



Fig. 25 (inset). Wrong way to apply coverslip to balsam wholemount. 



to one side. Mounts in natural balsam are 

 better put away for a month or two before 

 any attempt is made to clean them. The 

 slide should be cleaned, when it is suffi- 

 ciently hard, first by chipping off any ex- 

 cess balsam with a knife and secondly by 

 wiping away the chips with a rag moist- 

 ened in 90% alcohol. This will leave over 

 the surface of the slide a whitish film 

 w^hich may then be removed with a warm 

 soap solution, and the sHde may be pol- 

 ished before being labeled. 



The writer prefers to apply a ring of 

 some cement or varnish round the edge 



of his balsam mounts for two reasons. In 

 the first place such a ring diminishes the 

 rate of oxidation so that the mounts do not 

 start going brown around the edges. In the 

 second place, such shdes are less Ukely to 

 be damaged in students' hands because of 

 the psychological effect produced by a 

 well-finished shde. One must carefully 

 avoid using any cement or varnish which 

 is soluble in, or miscible with, balsam; the 

 author prefers to use one of the numerous 

 cellulose acetate lacquers which are avail- 

 able on the market. The method of apply- 

 ing such a ring has been described in 



