Method for making stained glass photomasks using stabilized glass

In a method of producing a precise stained pattern in a sheet of glass wherein a source of stained-producing ions is applied to a surface of a transparent sheet of glass having an established fictive temperature, stain-producing ions are migrated from said source into patterned areas of the glass sheet, and the glass sheet is then heated to a staining temperature range at which the migrated ions develop coloration within the glass sheet and at which the glass sheet remains essentially uncrystallized, and during said heating step a difference between the established fictive temperature of the glass sheet and the staining temperature range leads to undesirable dimensional changes in the glass sheet, the improvement comprising:

• prior to the application of the source of stain-producing ions onto the glass sheet, reducing the difference between the fictive temperature of the glass sheet and the staining temperature range by subjecting the glass sheet to a preliminary heat treatment at a temperature at which the fictive temperature of the glass sheet is substantially changed in the direction of the staining temperature range and essentially no crystallization of the glass sheet occurs, whereby dimensional stability of the glass sheet during the subsequent color development heat treatment step is improved.