This method consists of determining the mass of a specimen in air and subsequently immersing it in water. The apparent mass of a sample upon immersion in water is determined and its specific gravity calculated. This test method is based on ASTM D792 Standard Test Method for Density and Specific Gravity (Relative Density).
Sample size is 20-50 gram and any loose pieces should be removed before weighing and immersing. If material is lost during weighing the test is restarted. Two pieces per sample are measured to show variance and to identify samples to be rechecked. Samples are to be rechecked if the variance between the Specific Gravities for the 2 samples is greater or equal to 0.075. Temperature of water and sample must be at 23 °C +/- 2 °C.
The Calculation of specific gravity is as follows:
Sp gr 23/23 °C = a/(a+w-b)
a = apparent mass of specimen, without wire or sinker in air
b = apparent mass of specimen (and of sinker, if used) completely immersed in water.
w = apparent mass of totally immersed sinker if used and wire.