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US 5,030,594 AGranted
Highly transparent, edge colored glass
AssigneePPG Industries, Inc.
InventorRobert B. Heithoff
Life of this patent
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Abstract
A clear glass, with the substantial absence of color in transmittance, and with an attractive, bright, pure azure edge coloration is achieved in a glass having greater than 87 percent, preferably greater than 90 percent, luminous transmittance by using very small amounts of iron oxide as the sole essential colorant, with the ratio of iron in the ferrous state to total iron being at least 0.4.
Claims16
Clear glass with pure edge coloration comprising a soda-lime-silica base glass portion comprising:
- ______________________________________ Weight % ______________________________________ SiO.sub.2 66-75 Na.sub.2 O 12-20 CaO 7-12 MgO 0-5 Al.sub.2 O.sub.3 0-4 K.sub.2 O 0-3 ______________________________________
- and a colorant portion consisting essentially of iron oxide in an amount less than 0.02 percent by weight of the glass expressed as Fe.sub.2 O.sub.3, the ratio of iron present in the glass in the ferrous state expressed as FeO to the total amount of iron in the glass expressed as Fe.sub.2 O.sub.3 being at least 0.4, whereby the glass exhibits luminous transmittance (illuminant C) of at least 87 percent at a thickness of 0.223 inches (5.66 millimeters), the colorant portion including all essential colorants in the glass.
A method of making clear glass having pure edge coloration comprising:
- feeding batch materials to a melting stage of a glassmaking operation, the batch materials being selected to provide in the final glass product having the following base glass composition:
- ______________________________________ Weight % ______________________________________ SiO.sub.2 66-75 Na.sub.2 O 12-20 CaO 7-12 MgO 0-5 Al.sub.2 O.sub.3 0-4 K.sub.2 O 0-3 ______________________________________
- and a total iron oxide content of no more than 0.02 percent by weight expressed as Fe.sub.2 O.sub.3 ;
- providing to the glassmaking operation no significant colorant other than iron;
- controlling redox conditions in the glassmaking operation to maintain the ratio of iron present in the glass in the ferrous state expressed as FeO to the total amount of iron in the glass expressed as Fe.sub.2 O.sub.3 equal to or greater than 0.4;
- and forming the glass into a clear glass product, whereby the glass has luminous transmittance (illuminant C) of at least 87 percent at a thickness of 0.223 inches (5.66 millimeters).
3 more elements
Dependencies are inferred from the claim text.