Method for producing a coated component of quartz glass or fused silica

A method for producing a coated component consisting of transparent or opaque fused silica comprises a method step in which a SiO2 granulation layer is applied to a coating surface of a substrate, which in the area of the free surface has a relatively great granulation fine fraction. Starting from this, in order to achieve a smooth, preferably also dense surface layer, it is suggested according to the invention that the application of the SiO2 granulation layer comprises (i) providing a dispersion containing a dispersion liquid and amorphous SiO2 particles which form a coarse fraction with particle sizes ranging between 1 μm and 50 μm and a fine fraction of SiO2 nanoparticles having particle sizes of less than 100 nm, wherein the solids content of the dispersion is between 70 and 80 wt.-%, and of which between 2 wt.-% and 15 wt.-% are the SiO2 nanoparticles, (ii) applying the dispersion to the coating surface by casting or spraying it thereonto so as to form a slurry layer having a layer thickness of at least 0.3 mm; and (iii) drying the slurry layer by removing the dispersion liquid at a rate and in a direction such that under the action of the dispersion liquid being removed the fine fraction is enriched in the outer portion of the granulation layer, thereby forming a casting skin.