The invention relates to a process of treating parts of the surface of a porous dental ceramic article comprising the steps of: a) providing a composition and a porous dental ceramic article having an outer surface, b) applying the composition to only a part of the outer surface of the porous dental ceramic article, c) optionally drying the porous dental ceramic article, and d) optionally firing the porous dental ceramic article, the composition comprising: a liquid being miscible with water, but not being water, a whitening agent comprising nano-sized metal oxide particles, metal ion containing components or mixtures thereof, a stabilizer (e.g. acid, base, complexing agent or mixture thereof). the porous dental ceramic article showing a N2 adsorption and/or desorption of isotherm type IV according to IUPAC classification. The invention also relates to a dental ceramic article obtainable by a process.