Floatless colorless glass and floated ultra-white glass In terms of appearance, the biggest difference is transparency. The former is not strictly required. Usually the visible light transmittance is 89% (3mm), while the ultra-white has strict requirements. It also has strict regulations on the iron oxide content that causes the glass to be colored (blue and green): the visible light transmittance is not low. At 91.5% (3mm), the content of iron oxide (Fe2O3) is not higher than 0.015% (ordinary float is about 0.1%, which is 10 times higher).