Patent ID: 6250110
Filing Date: 2001-06-26
Classification: C03C,Y10S

Abstract:
A nitrate-free method for manufacturing a dark bronze glass composition and improving the ultra violet and infra red absorption thereof without consequently decreasing the visible transmittance of the glass, which method comprises the steps of:adding, during molten glass formation, colorants consisting essentially of iron oxide, manganese compound, selenium compound, and optionally cobalt compound to a soda-lime-silica base glass composition, and adding no sodium or potassium nitrate into the batch during molten glass formation, all base materials and colorants being used in sufficient quantities to manufacture a dark bronze glass composition whose base glass composition comprises: 68 to 75% SiO.sub.2, 10 to 18% Na.sub.2 O, 5 to 15% CaO, 0 to 10% MgO, 0 to 5% Al.sub.2 O.sub.3, and 0 to 5% K.sub.2 O, where CaO+MgO is 6 to 15% and Na.sub.2 O+K.sub.2 O is 10 to 20%; and colorants consist essentially of: greater than 0.5 to 1.5 wt. % total iron oxide as Fe.sub.2 O.sub.3, 0.1 to 1.0 wt. % manganese oxide as MnO.sub.2 ; 0.0 to 0.016 wt. % cobalt oxide as Co, and 0.0005 to 0.004 wt. % selenium as Se, all by weight percent based on the total weight of the bronze glass composition; the glass having at a 4.0 mm. thickness: 570-585 dominant wavelength; 20 to 65% light transmittance using Illuminant A (LTA), wherein up to 50% LTA the excitation purity is 7-30%, and above 50% LTA, the excitation purity is 5-20%; less than 35% ultra violet transmittance measured over 300-400 nm, and less than 46% infra red transmittance measured over 760-2120 nm; andmaintaining the oxidation properties of the glass batch so as to provide a bronze glass wherein the ratio of wt. % FeO/wt. % total iron as Fe.sub.2 O.sub.3 is below 0.26.