P2O5 is a glass network former like boric oxide and silicon dioxide. Phosphoric glass tends to show as a bluish flush in glazes. It does not enter the silica chain in the matrix. However, P2O5 by itself (with no SiO2 present in the matrix) is a glass former and the base of an entire class of glasses that can be doped with rare earths and metals for produce special purposes ranging from soluble medical implants to insoluble acid-resistance and even radiation resistance.