The GLOBE Specific Gravity Balance provides a simple and quick mean to read directly the specific gravity of rubber and other elastomers, thus reducing labour and eliminating calculations. The time taken to find out the specific gravity of a sample is only about half a minute.The balance consists of an anodised scale with specific gravity (SG) printed on it standing vertically on a heavy base plate. A balancing arm is provided at the centre point of the scale. The arm is supported on two jewel bearings to minimise friction.
Two stainless steel pins are suspended from one end of the arm. One of the pins is attached through a short length of yarn and the other through a long length of yarn. The second pin is kept immersed in water inside a tall transparent jar kept on the base.
A pointer is attached at the other end of the balancing arm that indicates the specific gravity of sample under test. A sliding weight is also provided for initial balancing of the samples of different weights. A levelling screw is provided for initial levelling of the base plate.
A sample of any shape can be used for determination of specific gravity. Its weight shall, however, lie between 5 and 15 g. The sample used shall not be soluble in water or be affected by it in any way. If the sample has a cellular structure, the cells shall be of closed type so that the absorption of water is kept at minimum.
Other models of specific gravity balance capable of measuring specific gravity in the range of 0.2 to 2.0, 0.05 to 0.70, and 0.02 to 0.50 are also available. Special models for measurement of specific gravity of liquids and of materials in form of powder or granules are also being manufactured.