Ceramic clay is a composition of different chemicals, chemically extracted inorganic minerals and metallic and nonmetallic elements so it needs to be fired to higher temperatures to fuse together all these separate elements.
Pure-clay is one single entity just as it is found in nature. All the nutrients in the clay are already bonded together. The firing in this case is to eliminate water from its molecular structure. Since it’s already one body the clay gets vitrified quickly at lower temperatures — another reason why Pure-clay is a more eco-friendly option!