| 摘要 |
This invention is directed to a method for modifying the coloration produced in a silver halide-containing photochromic glass when heat treating the glass at a temperature not exceeding 450 DEG C. under reducing conditions. The method comprises subjecting such a glass having a base composition which contains at least 1% by weight Li2O, at least 2% by weight Na2O, and at least 6% by weight Li2O+Na2O+K2O to an ion exchange reaction, wherein lithium ions, and potassium ions, when the latter are present in the composition, in the glass surface are exchanged with sodium ions from an external source, prior to the reduction heat treatment.
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