Embedding xvitli Paraffin 



37 



Figures 1, 2, and 3 



Folding a bond paper or 

 an aluminum foil box for 

 paraffin embedding. 



offers an embedding combination with 20 or 30 compartments. The 

 literature and catalogs are full of ideas; the above are just a few of them. 

 When small amounts of paraffin are ready to be solidified, they can be 

 cooled immediately in water, preferably at a temperature of 10-15°C. 

 Make certain that a solidified scum has formed over each potential block 

 before dipping it below the surface of the water. Water colder than 

 10°C causes the block to contract too strongly and it may finally crack. 

 Furthermore, normal crystals may form in the center, but abnormal 

 ones in the periphery of the block. The perfect block is one in which the 

 paraffin crystals are contiguous with each other and the paraffin appears 

 clear and homogeneous. Paraffin may contain 7-15% air dissolved in it 

 and will appear clear Avhen that air is distributed evenly through its 

 mass. But pockets of air produce milky spots, a condition called "crystal- 

 lization." Either slow hardening of the block in the air, or too rapid 

 cooling may cause this effect, particularly in the case of large blocks. 



