Knoop Hardness Test

The Knoop hardness test is a test for micro-hardness test.  It is used to test materials which are extremely brittle.  The indentor in the Knoop hardness test is a pyramidal diamond point.  A known load of 100 grams is pressed against the specimen. 

The hardness test is given by

HK = Load/ (Correction Factor x Area of the impression in

The correction factor is unique to the shape of the indentor and is provided by the manufacturer of the test apparatus.

The advantages of this test are that only a small specimen is required.  A microscope is required to measure the dimensions of the indentation.