Patent ID: 7811508

Claim:
Coloration process for obtaining on the surface and/or in the interior of fired ceramic material a variation in the resultant colour of iron-based colorant solutions comprising: (a) adding to a ceramic mix from 1% to 15% by weight with respect to the dry ceramic mix, precipitated silica and/or silica gel having an active surface S≧100 m 2 /g at the moment of coloration, said active surface S being defined by the formula S=A*Gr , where: Gr is the particle size fraction comprised between 5 and 60 microns for precipitated silica and between 1 and 60 microns for silica gel, and A is the surface area of the silica expressed in m 2 /g measured by the B.E.T. method; (b) applying to the surface of the additive-containing ceramic mix aqueous or organic solutions comprising inorganic salts of Fe(II) and/or Fe (III), or organic derivatives of Fe(II) and/or Fe(III); (c) providing a variation in the resultant colour being equal to ΔE>6.