An opaque zone in the polycrystalline (PCA) discharge vessel of a high intensity discharge lamp may be made by creating residual pores in predetermined regions of the final-sintered discharge vessel. The control over the placement of the opaque zone is achieved by forming a carbonaceous residue in a specific region of the discharge vessel prior to final sintering. During sintering, the carbonaceous material causes residual porosity in the sintered PCA. The higher emissivity of the opaque PCA provides localized cooling in order to provide more control over the condensate behavior in the discharge vessel.