NGK succeeded to develop a new heat-resistant material of high density, "NEWSIC", which is mainly made of SiC. NEWSIC has superior acid corrosion-resistance and durability, therefore, it withstands the long use at high temperature. NEWSIC is also outstanding for its super high strength, which is five times as strong as the former materials of SiC heat-resistant refractories. This makes it possible to thin the refractory walls; as a result, the lightweight refractories become available. NEWSIC is indispensable to the shelves in the furnace.