PEI – Porcelain Enamel Institute. English laboratory that created the procedure to assess the resistance that the enamel layer will have to the flow of people and contact with abrasive dirt on a daily basis.

 

MOHS – In 1812, the German mineralogist Friedrich Mohs created the scale with 10 minerals of different hardnesses existing in the Earth’s crust, being the talc of less hardness - with hardness 1 - and diamond with hardness 10, the greatest hardness found in nature.