Fundamentals of Dental Materials

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Dental Materials

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Dental Resins, Miscellaneous Dental Materials, and Dental Gold/Alloys

2-16. FINENESS, CARAT, AND WEIGHING

The amount of gold in a gold alloy may be rated in terms of fineness or carat. Fineness is determined by the parts per thousand of pure gold contained in the alloy. In terms of fineness, pure gold is 1,000 fine, and an alloy with three-fourths pure gold is 750 fine. In the carat system of rating, the carat refers to the parts of gold determined by dividing the substance into 24 units and then counting the number of units of gold. Thus, a 24-carat substance would be pure gold and a 12-carat alloy would be one- half gold. In weighing precious metals like gold and platinum, the troy system of weight is used. In this system, the basic units of measurement of alloy quantity are grains, pennyweights, and ounces. Gold alloys are recorded and issued by the troy system as indicated in Table 2-1.

24 grains (gr) = 1 pennyweight (dwt)

20 pennyweight (dwt) = 1 ounce (oz)

12 ounces (oz) = 1 pound (lb)

The conversion formula for carat to fineness is:

carat = fineness

24 1000

Table 2-1. Troy system of weight.

Primary Content Providers: The U. S. Army, The U.S. Navy
Ancillary Content and Online Version: David L. Heiserman
Publisher: SweetHaven Publishing Services