Patent ID: 7033427

Claim:
A composition for colouring the surface of a porous substrate, the composition comprising: (i) a colorant, which is a metal oxide or a mixture of metal oxides, wherein the colorant has a particle size of between about 0.1 microns and about 100 microns. (ii) a binding agent to cause binding of the composition to the substrate, wherein the binding agent is tetraethyl silicate, and (iii) a water-repelling agent selected from the group consisting of a. liquid fluorocarbons, b. alkyl alkoxy silanes and a catalyst therefor, c. alkyl alkoxy siloxanes and a catalyst therefor, and d. mixtures of alkyl alkoxy silanes, alkyl alkoxy siloxanes and a catalyst therefor, and the composition being formulated whereby, on application of the composition to the surface of the porous substrate, the composition penetrates the surface through the pores of the substrate, and colors the surface of the porous substrate.