Process for colouring ceramic materials

Abstract

The invention relates to a new process for colouring ceramic materials by using aqueous solutions of chromophore ions. In particular, certain types of silica are added to the ceramic mixes which are to be coloured, after which aqueous or organic solutions comprising inorganic salts of Fe(II) and/or Fe (III), or organic derivatives of Fe (II) and/or Fe (III) are applied to the surface of the said additive-containing ceramic mixes.

1 - 23 . (canceled) 
     
     
         24 . Totally or partially decorated ceramic material obtainable in accordance with a 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, wherein the silica in the form of granules and the surrounding ceramic material are both colored by the Fe-based solutions.   
     
     
         25 . Totally or partially decorated ceramic material obtainable in accordance with a 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;   (d) treating the additive-containing ceramic material with aqueous solutions containing from 0.1% to 20% by weight of iron (expressed as elemental Fe) in the form of inorganic salts of Fe(II) and/or Fe (III), or organic derivatives of Fe(II) and/or Fe(III), wherein the silica in the form of granules and the surrounding ceramic material are both colored by the Fe-based solutions.   
     
     
         26 . Decorated ceramic material as claimed in  claim 24 , further comprising subjecting the surface after firing to satinizing, smoothing, polishing or lapping. 
     
     
         27 . Decorated ceramic material as claimed in  claim 26  comprising porcelain stoneware. 
     
     
         28 . Decorated ceramic material as claimed in  claim 25 , the surface of which has been subjected after firing to satinizing, smoothing, polishing or lapping. 
     
     
         29 . Decorated ceramic material as claimed in  claim 28  which is of porcelain stoneware.