MOTHER-OF-PEARL AND BLISTER PEARLS 



135 



washed with water and pumice stone or sand. Then they are ground on an emery 

 wheel to remove horny backs and provide a uniform thickness. Finally, they 

 are again soaked in water which softens them for the finishing machine. 



The more modern factories use an automatic machine which rounds the edges 

 of the buttons, carves out the center in the desired pattern for the face, and drills 



Fig. 8-5. Sorting or grading 

 finished buttons. 



(Courtesy American Pearl 

 Button Co.) 



2 or 4 holes according to pattern. These machines finish from 30 to 70 buttons 

 a minute, thus making from 100 to 190 gross per day. 



The drilled buttons are again placed in churns and cleaned with water and 

 pumice in preparation for the final polish. This latter is a tumbling process in 

 which sulfuric acid or other acid is used in conjunction with steam. Finally, the 

 buttons are carefully sorted into 12 grades, and those intended for retail trade 

 sewed on cards. 



Manufacture of Inlaid Objects 



Because it is at the same time hard and splintery, mother-of-pearl is difficult 

 to process. The initial operation consists of freeing the shells from the outer cover- 

 ing, or "bark." This can be done either before or after they have been divided 

 into separate pieces for ornamental use. In button manufacture the outer coating is 

 usually removed afterwards, while in other cases it is removed before the shell 

 is cut up. 



In separating the shells into sections care is taken to secure pieces of good 

 quality and adequate size; only after long practice does the workman acquire the 

 art of doing this properly. The cutting is done with a circular saw of well- 

 tempered steel, the operation facilitated by the use of emery. After the pieces have 

 been cut perpendicular to the surface, it may be necessaiy to divide them hori- 

 zontally into thin plates; however, these are more usually secured from the thinner 

 parts of the shell near the lip, while thicker pieces are obtained from that part 

 which is near the hinge. Since the thickness of the nacreous stratum varies in 



