In a known method for producing an SiO2 blank, SiO2 particles are formed in a burner flame of a deposition burner and are deposited under the effect of an electrical field on a substrate. Starting therefrom, in order to indicate a simple and inexpensive method by means of which blanks can be produced with a predetermined, in particular axially homogeneous, mass and density distribution, it is suggested according to the invention that the geometrical shape of the burner flame (8) is adjusted by the effect of the electrical field (9) in dependence upon the geometrical parameter of a deposition surface (12; 21) of the substrate (1) that is assigned to the burner flame (8). An apparatus suited for performing the method comprises a substrate, at least one deposition burner for producing SiO2 particles in a burner flame assigned to the deposition burner, a measuring device for sensing a geometrical parameter in the area of a deposition surface of the SiO2 blank, and a pair of electrodes connected to a source of voltage for producing an electrical field (9) which is operative in the area of the burner flame and is adjustable in dependence upon the geometrical parameter of that deposition surface (21; 21) of the substrate that is assigned to the burner flame (8).