The six main hardness scales are the Rockwell hardness scale, the Vickers hardness scale, the Brinell hardness scale, the Mohs hardness scale, the Knoop hardness scale, and the Shore hardness scale. While there is no one reason why there are so many different ways to test and measure hardness, one explanation relates to technological advancement over time and the particulars involved in any measurement situation. Some of the older hardness scales, such as the Brinell hardness scale, may be reliable to use, but come with disadvantages like the slowness to complete the test. Additionally, some of the hardness scales are simply not suited to certain kinds of hardness measurement. If you are working with thin, small, or delicate materials you will need to choose either the Vickers hardness scale or the Knoop hardness scale, as these utilize less force than the others. If you are completing a great number of hardness measurements, the Rockwell hardness scale is probably the best choice due to its speed and accuracy. Depending on the type of hardness measurement you are completing, the hardness scale you should use will change.