The term float glass refers to a method of glass production that involves floating molten glass on top of molten tin. This technique, invented in the 1950s, results in a flat, smooth surface that is ideal for various applications. French green float glass, specifically, is produced through this method, whereby the incorporation of iron oxide lends it a subtle green tint. This coloration varies, depending on the thickness of the glass and the specific manufacturing process, resulting in a spectrum that ranges from a soft emerald to a deeper forest green.