US Patent 7404302 Method of depositing glass soot

A method for deposition glass soot for making an optical fiber preform. A fuel and a glass precursor are flowed to a burner flame forming glass soot which is deposited onto a glass target. By first depositing an insulating layer of glass soot with a low velocity burner flame, the amount of water which may be adsorbed into the surface of the glass target can be reduced. Thereafter, the flame velocity may be increased to increase the deposition rate of the glass soot without significantly increasing the concentration of water incorporated into the glass target.