122 MARINE PRODUCTS OF COMMERCE 



concentrated lacquer is used, it may be mixed with a clear lacquer containing ap- 

 proximately 10 per cent nitrocellulose. 



In effecting the actual dipping operation a "toothpick" is pushed into the 

 center of each bead. As many as 500 toothpicks with a bead affixed to each are 

 put into holes in large dipping boards. One or two boards with beads on the 

 underside are lowered until the beads are submerged in the pearl lacquer. After a 

 moment the boards are raised, removed from the dipping frame, examined, and 

 mounted on a machine which rotates them slowly to insure an even coat while 

 drying. Each dip takes from 1 to 2M hours to dry. When dry, the coated beads are 

 dipped again. The cheaper imitation pearls are given 4 or 5 dips, whereas the 

 high grade ones receive 8 or 10 dips. The rooms in which the dipping is carried 

 out should be free from dust and preferably air-conditioned. 



Threading and Clasping. The final step in the production is threading and 

 clasping. The imitation pearls are graded and matched, then strung on strong 

 thread. Double nylon thread is used for the best necklaces. 



Colors. Imitation pearls are made in a wide variety of colors: rose, pink, cream, 

 white, grayish white, orchid, peach, yellow, green, various shades of blue, bronze, 

 gunmetal, and black. These colors are imparted by tinting the lacquers with dyes. 



Other Uses for Pearl Essence. Lacquers and plastics containing pearl essence 

 are used to decorate many articles: mirror backs, manicure and toilet sets, jewelry 

 boxes, umbrella handles, opera-glass handles, electric light switches, automobile 

 dashboard fixtures, etc. 



REFERENCES 



Pearls 



Alexander, A. E., "Pearls through Artifice," Sci. Aj7i., 160, No. 4, 228-229 (1939). 

 Alexander, A. E., "Science Dissects the Peari," Sci. Am., 160, No. 5, 294-297 (1939). 

 Alexander, A. E., "Pead Formation Induced by a Rotifer," Am. J. Sci., 237, 920-922 



(1939). 

 Alexander, A. E., "An X-ray Study of Aragonite in Natural and Cultured Pearls," Am. J. 



Sci., 238, 366-371 (1940). 

 Alexander, A. E., "The Radiography of Cultured and Natural Pearls," The Gemmologist, 



10, No. 113, 45-48 (1940). 

 Alexander, A. E., "The Rate of Seasonal Deposition of Pearl Aragonite," Science, 93, 



No. 2405, 110-111 (1941). 

 Alexander, A. E., "Natural and Cultured Pearl Differentiation," Gems and Gemology, 



3, No. 1, 2, 169-172, 184-188 (1941). 

 Alexander, A. E., "The Mineralogy of Five Unusual Natural Pearls," The Gemmologist, 



10, No. 119, 93, 96 (1941). 

 Alexander, A. E., "Fossil Pearls," Sci. Am., 165, No. 2, 85 (1941). 

 Alexander, A. E., "All Pearls Are Not What They Seem," /. Gemmologij, 1, No. 1, 2-4 



(1947). 

 Alexander, A. E., "Baroque Cultured Pearls," The Gemmologist, 17, No. 201, 95 (1948). 

 Alexander, A. E., "Spectroscopic Investigation of Pearls," The Gemmologist, 17, No. 203, 



134 (1948). 

 Alexander, A. E., "A Fabulous Genuine Pead," The Gemmologist, 17, No. 208, 282- 



283 (1948). 

 Alexander, A. E., "Care and Treatment of Pearls," Jewelry Magazine, 5, No. 9, 46-47 



(1948). 



