Mason Stain 6310. Produces strong cobalt/royal blues in most glazes up to 2300 F. Blend with a zircon opacifier (Ultrox or Zircopax) to lighten with ZrV blue stain for warmer hues with CrSn crimsons/pinks (up to cone 6) for purples and mauves or with CrCo greens for blue-greens. May be used as a body stain. Composition - CoAlZSi