The hardness of a substance is generally measured using one of two scales that determine how easy it is to scratch or dent. The earliest scale for measuring hardness was developed in the early 1800s and required the use of common tools like copper pennies, steel files, and a fingernail that could be used to scratch the surface of materials. A later scale, called the Rockwell scale, was developed in 1908. This method uses an industrial press to make indentations on a substance.
The Mohs Hardness Scale
This scale was developed in the nineteenth century but a German mineralogist who wanted to classify the hardness of different rocks, minerals, and gems. The scale goes from 1 to 10, with one being the softest and ten the hardest. In order to determine the place of a mineral on the scale, the tester attempts to scratch a surface of the substance with a different substance. Materials of equal or greater softness can be scratched, while harder materials resist scratching. The results of the test are more general than exact, because hardness often depends on the purity of a mineral sample as well as other factors.
The Rockwell Scale
The modular Rockwell hardness tester clears up a lot of the uncertainty associated with the Mohs scale. Since it uses a special pressing tool rather than a collection of files and other objects that might vary from person to person, it allows for a more accurate reading that is able to be replicated in multiple tests. A Rockwell scale press works by applying two separate loads to an item, one very light one and one that is more heavy. A reading is taken by measuring the difference between the indentation made by the light load and the one made by the heavy one.
The Mohs scale is useful for informal testing because it does not require a lot of specialized equipment. However, it does not provide results that are as accurate as the Rockwell scale which uses special testing tools.
If you are reading this on any other blog than G&R Technology Inc. or via our RSS Feed, it is stolen content without credit.
Come and visit our blog at http://www.grhardnesstester.com/blog/