Method of producing uniform light transmission fusion drawn glass

Abstract

In a method of making a glass sheet using an overflow fusion downdraw process, a glass sheet quality metric level Qis selected, where Qis a measure of allowable retardation in the glass sheet. A glass ribbon temperature Tat which a potential glass ribbon thermal artifact could occur in a glass ribbon while the glass ribbon is being drawn through a drawing machine enclosure is identified. A thermal artifact envelope Eis determined, where Econtains types of glass ribbon thermal artifacts allowable at Tand Q. A glass melt is overflowed from an isopipe to form a glass ribbon at the root of the isopipe. The glass ribbon is drawn below the root of the isopipe through the drawing machine enclosure to form the glass sheet. The drawing machine enclosure is altered at a location corresponding to where the glass ribbon would be at Tsuch that during drawing of the glass ribbon the potential glass ribbon thermal artifact is not formed in the glass ribbon at Tor, if the potential glass ribbon thermal artifact is formed in the glass ribbon at T, the potential glass ribbon thermal artifact is within E.