A method of making a fused silica article having a combined concentration of protium and deuterium in a range from about 1×1016 molecules/cm3 up to about 6×1019 molecules/cm3. In some embodiments, deuterium is present in an amount greater than its natural isotopic abundance. The method includes the steps of providing a fused silica boule, diffusing at least one of protium and deuterium into the boule, and annealing the boule to form the fused silica article. A method of diffusing hydrogen into fused silica and a fused silica article loaded with hydrogen formed by the method are also described.