How to Modify a Powder Scale for Specific Gravity Testing

How to Use a Powder Scale

You can find both electronic and beam-type powder scales for sale. The beam-type RCBS Model 505, available through Amazon, is highly recommended and inexpensive. (We’ll use the beam-type scale as our example). Powder scales uses “grains” as a unit of measure. One carat equals 0.324 grains.

As with any beam scale, you must zero a powder scale before weighing anything on the pan. Adjust the tenth, one, and ten-grain weights on the beam until the marker opposite the pan sits at zero before every measurement.

In gemology, specific gravity or density is the ratio of the weight of a gemstone to the weight of an equal volume of water. To determine the specific gravity of a gemstone requires two measurements: the weight of a gemstone in air and the weight of a gemstone underwater.

Plug those measurements into the following formula and you have the gem’s specific gravity:

Weighing a gemstone in air is easy enough with a powder scale. (Don’t forget to clean your gemstone first). With a simple modification, you can use also it to weigh a gemstone underwater

How to Modify a Powder Scale for Underwater Measurements

You’ll need to…