Polyester Embedding 87 



Allow to harden at room temperature: 12-24 hours. Peel off capsule 

 or dissolve it in warm water. If the resin cures too rapidly or too 

 slowly, the catalyst and promoter may be decreased or increased by 

 one drop of each. 



SECTIONING 



If the block is made long enough, the block itself can be clamped 

 directly in the tissue carrier. Slow cutting usually produces the best 

 sections. Ueckert {I960) recommends the sledge microtome as best for 

 polyester sectioning, but most laboratories do not possess this type of 

 microtome and will have to resort to the use of a rotary type. Sometimes 

 breathing on the surface of the block facilitates sectioning. If the sec- 

 tions curl, the knife is dull or the knife angle is incorrect. 



STAINING 



Place the sections after cutting in distilled water. Stain them im- 

 mounted, because mounted sections trap the stain under the plastic 

 which is never removed. 



Kuhn and Lutz recommend safranin and fast green dissolved in 

 alcohol. Ueckert has used hematoxylin-eosin, iron hematoxylin-Van 

 Gieson, and silver methods. Follow the staining by floating the sections 

 on absolute alcohol to remove any excess stain. Blot and mount in 

 Permount or any similar moimtant (page 416). Do not use toluene; it 

 causes the plastic to swell and form wrinkles. 



Kuhn and Lutz have used this method for whole decalcified snake 

 heads, chick embryos, leg joints and luidecalcified mouse paw and tail; 

 they suggest the possibility of its use for plant material. 



