Crock Meter Tester
One of the tests for determination of colourfastness of dyed leather is the crocking test. This test is used for the determination of colourfastness against rubbing, either under dry or under wet conditions.
In this test a moving brass finger of specified shape and size rubs against the test specimens under a fixed load. The amount of colour lost by the sample under test and the amount of colour transferred to a piece of abradant fabric fixed over the base of the moving finger are graded with the help of standard grey scales to evaluate the colour fastness against rubbing.
The GLOBE Crockmeter consists of a rigid flat metallic platform on which the test specimen can be held firmly and an abrading finger that rubs against it under a specified load. The platform is fixed over the base of the equipment and lies in a horizontal plane. The test specimen is held firmly over an abrasive paper, which is pasted on the upper face of the platform, with the help of two plates holding it at both ends.
The abrading finger has a flat circular rubbing face, which is covered with a piece of white abradant fabric during the test. The abradant fabric picks up colour lost by the test specimen during rubbing. It is held over the finger with the help of a tapered ring.
Motion to the finger is given through a reciprocating arm, which runs on two ballÃ‚Âbearings to minimize friction and to apply a uniform load on the finger. The arm is moved by a manually operated crank and connecting link.
The equipment is finished in shore blue matalic painting and bright chrome plating to give it a corrosion resistant finish.
A motorized model in which the motion to the rubbing finger is given by a synchoÃ‚Â set type motor operating at a speed of 60 rpm is also available.
Grey scale for change in colour and grey scale for staining, needed to evaluate the results of the test, are available as optional accessories.
|Diameter of the finger |
|16 mm |
|Load on the finger |
|150 g (force of 0.075 kgf / cm2) |
|Length of travel of the finger |
|100 +- 12 mm |
|Dimensions of the test specimen |
|125 x 50 mm |
|Related Standards |
|IS 6191 - 1971 |
|Methods of Micro - Biological Colour Fastness and |
Microscopical Tests for Leather