| 摘要 |
PROBLEM TO BE SOLVED: To effectively prevent the change in oxidation number of glass components or to extremely reduce the change in the oxidation number even in the case that the oxidation number is changed when glass powder is further heated or thermally post-treated by previously adding a specific amount of a thermally active and nonpoisonous oxidant or reducing agent in the state of solid, liquid or gas to the glass powder. SOLUTION: At least one oxidant or reducing agent is added into glass powder, especially, dental glass powder. As the oxidant or reducing agent, a thermally active and nonpoisonous compound such as NH4Cl is preferably used, and a preferable amount of the agent to be added is 0.01 to 1 wt.%, preferably 0.5 wt.%. Thereby, it becomes possible to suppress the change in the oxidation number of polyvalent positive ions, or the like, contained in the glass powder to be minimum when the glass powder is further treated or thermally post- treated. Accordingly, the change of color components contained in the powder can be suppressed at the treatment such as melting or purification of the powder, and color change is sanitarily and ecologically safely avoided and the deterioration in the quality of the glass powder can be inhibited.
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