The invention relates to a process for selectively treating parts of the surface of a porous dental zirconia article, the process comprising the steps of providing a liquid composition and a porous 3-dimensional dental zirconia article having an outer and inner surface, applying the liquid composition to only a part the outer surface and/or inner surface of the porous dental zirconia article, the liquid composition comprising a whitening agent comprising a phosphorous containing component, the phosphorous containing component comprising a phosphate, phosphone or phosphine moiety, with the proviso that at least one P—O unit of the phosphate, phosphone or phosphine moiety is dissociable or able to otherwise interact with zirconia. The invention also relates to a dental zirconia article obtainable or obtained by such a process and a kit of parts comprising a container containing a certain liquid composition.