Silver stains: The higher the temperature / the longer the soak time, the deeper the silver stain color. Silver stain is darker on the tin side of float glass. If silver stain has been fired and is not dark enough, it may be reapplied over the same area and fired again.
Silver stains should not be applied over other paints that have been previously fired (such as grisailles) but paints may be applied over silver stains that have been fired. Wipe or wash the ochre residue off the glass after firing.