Low iron oxide glass has no green tint or shimmer. When sunlight hits ordinary glass, all colour components (blue, yellow, red, etc.) are absorbed or filtered, except for a residual green cast. The reason for this is the quartz sand containing iron oxide in the glass mixture used to make the glass. With conventional glass, the iron oxide content is around 800 ppm (parts per million). The thicker the glass is, the more this is visually noticeable. If, on the other hand, raw materials low in iron oxide are used to melt the glass, the iron oxide content can be reduced to below 200 ppm. The result is the so-called white glass or also called extra white. This is characterised by a very colour-neutral transparency and has no green tint.