Hardness
A quality index of water, which reflects the salt-containing characteristics of water
A physical property of a mineral. The ability of a mineral to resist some external mechanical action, especially scribing. Mohs hardness is usually used to determine relative hardness.
The methods for measuring hardness include scratch method, press-in method, elastic rebound method, anti-wear method, etc. According to different measurement methods, different quantities can be used to represent hardness. The more well-known ones are: Brinell hardness, Rockwell hardness, Vickers hardness, Shore hardness, etc.
In the coatings industry, there have been some misunderstandings about the definition of hardness in the past. Most coatings are viscoelastic and therefore sag to some extent. Therefore, DIN55 945 defines hardness as follows:
Hardness is the resistance of a coating to mechanical forces such as pressure, friction and scratching.
