PRESERVATION OF SPECIMENS IN PLASTICS Q<J 



of the emulsion-paste type used for automobiles are suitable for this coat- 

 ing, as are also a number of other commercially available nonfluid prep- 

 arations that are specially offered for this purpose. Liquid waxes, on the 

 other hand, and others containing active solvents or other detrimental 

 ingredients, must be carefully avoided because of their tendencies to 

 scratch the surface or cause crazing. 



In applying this protective coating, the wax should be put on with a 

 damp cloth, and then polished vigorously with a piece of clean flannel or 

 other suitably soft woolen cloth until a high luster is obtained. 



CARE OF FINISHED MOUNTS 



Methaerylate plastic mounts are not affected by moisture or natural 

 temperature variations, and light has practically no effect upon them 

 except that it may alter the specimen colors when they have not been 

 fully stabilized before embedment. The mounts are, therefore, very dur- 

 able, and, if not subjected to careless handling or exposure to active sol- 

 vents or solvent vapors, they may be expected to retain their original 

 appearance almost indefinitely. They are somewhat easily scratched, 

 however, and for that reason should be kept coated with a thin protective 

 layer of wax and handled with reasonable care to avoid undue abrasion. It 

 is furthermore advisable to cover them with protective wrappings or 

 soft packing material when shipping or transporting them. 



Cleaning 



Whenever it becomes necessary to clean mounts of this type, it is best, 

 if possble, to do so with clear water or with water to which pure soap has 

 been added. Gritty soaps, as well as most types of synthetic detergents, 

 should be avoided. Ammonia water, however, may be used if needed to 

 remove grease and stains, and it is also safe to use kerosene or mineral 

 spirits for this purpose. Practically all other solvents, as well as solvent 

 cleaning mixtures not specifically designated for use on acrylic plastics, 

 should consistently be avoided because of their tendency to induce craz- 

 ing. In drying the blocks after cleaning, it is advisable to use soft tissue 

 paper or clean, soft cloth or chamois skin. Similar materials should also 

 be used when wiping off dust or nongritty dry dirt. 



After cleaning, it is always good practice to apply a new coating of 

 protective wax in the manner described in the preceding section. 



Refinishing 



In cases where blocks have become dull or scratched, they should first 

 be cleaned with mineral spirits or kerosene to remove the wax coating, 

 and then, if necessary, washed with soapy water. After this they can be 

 resurfaced by wet-sanding according to the procedure previously de- 

 scribed ; they "are then ready for polishing and waxing in the usual manner. 

 Minor scratches and abrasions can usually be eliminated satisfactorily 

 by the simple application of a new coating of wax followed by vigorous 

 polishing with a soft flannel cloth. 



Blocks in which crazing has developed can, in some cases, be satis- 

 factorily reclaimed by sanding them down or otherwise resurfacing them 



