boric acid is a common primary source of boric oxide (B2
) for production of frits for single-fired wall tiles and for lead-free frits.
borax pentahydrate’s purity; high, consistent level of boric oxide (B2
); and 21% sodium oxide (Na2
O) (a powerful flux) makes it a popular choice for frits for double firing and for floor-tile frits for which sodium is a benefit.