Method for producing synthetic quartz glass and synthetic quartz glass article

The first part of the invention provides a method for producing a synthetic quartz glass which has a reduced content of impurities, exhibits a high-temperature viscosity characteristics being the same as or superior to those of a natural quartz glass, and is less prone to deformation even in a high-temperature atmosphere, in particular, a dense and highly heat-resistant synthetic quartz glass containing no bubbles. The second part of the invention provides a method for producing a highly heat-resistant synthetic quartz glass, in particular, a dense transparent or black synthetic quartz glass containing no bubbles, exhibiting high absorbance and high emission rate for an infrared ray, and extremely high effect for the prevention of diffusion of an alkali metal. The method for producing the synthetic quartz glass having an absorbing coefficient at 245 nm of 0.05 cm-1 or greater comprises subjecting a porous silica material to a reducing treatment, and then firing the resultant product, to thereby form a dense g