SOLID SPECIFIC GRAVITY:
The solid specific gravity is not the same as the percent solid or pulp density. The solid density or solid specific gravity is the mass per unit volume of dry solid (kg/dm3 or kg/L or g/cm3). With the water density equal to 1, the solid density can be obtained from its weight and its volume as below:Put the dry solid in a 1 litre beaker of known tare and weigh. Fill up the beaker with water to the 1 litre mark, ensuring the solid particles are fully wet (wet the solids and mix before gradually adding the remaining water). The volume of solid is then equal to 1 litre minus the amount of added water.
To use:
An example can be seen on this Youtube video.