GS 



MISC. PUBLICATION 679, U. S. DEPT. OF AGRICULTURE 



Figure 16. — Specimens prepared by C. E. Sando show the clarity and luster obtain- 

 able through accurate machining and polishing of the finished blocks. 



slow rate. This method of polishing is time-consuming but it yields ex- 

 cellent results when properly carried out (fig. 16) . 



Waxing 



The polished surfaces can be given a fair degree of protection against 

 dirt and abrasion, and their maximum luster maintained for a longer 

 period, if they are covered with a durable wax coating. Polishing waxes 



