into sheet by an iron roller, the process being similar to that employed in making plate-glass, but on a smaller scale. The sheet thus rolled is roughly trimmed while hot and soft, so as to remove those portions of glass which have been spoiled by immediate contact with the ladle, and the sheet, still soft, is pushed into the open mouth of an annealing tunnel or temperature-controlled oven called a lehr, down which it is carried by a system of rollers. Polished plate glass The polished plate glass process starts with sheet or rolled plate glass. This glass is dimensionally inaccurate and often created visual distortions. These rough panes were ground flat and then polished clear. This was a fairly expensive process. Before the float process, mirrors were plate glass as sheet glass had visual distortions that were akin to those seen in amusement park or funfair mirrors. In 1918 the Belgian engineer Emil Bicheroux improved the plate glass manufacturing by pouring molten glass between two rollers, which resulted in more even thickness and less undulations, and reduced the need for grinding and polishing. This process was further improved in the US. Rolled plate (figured) glass The elaborate patterns found on figured (or 'Cathedral') rolled-plate glass are produced in a similar fashion to the rolled plate glass process except that the plate is cast between two rollers, one of which carries a pattern. On occasion, both rollers can carry a pattern. The pattern is impressed upon the sheet by a printing roller which is brought down upon the glass as it leaves the main rolls while still soft. This glass shows a pattern in high relief. The glass is then annealed in a lehr. The glass used for this purpose is typically whiter in colour than the clear glasses used for other applications. Only some of the figured glasses may be toughened, dependent on the depth of the embossed pattern. Single rolled figured glass, where the pattern is only imprinted into one surface, may be laminated to produce a safety glass. The much less common 'double rolled figured glass', where the pattern is embossed into both surfaces, can not be made into a safety glass but will already be thicker than average figured plate to accommodate both patterned faces. The finished thickness being dependent on the imprinted design. Float glass Ninety percent of the world's flat glass is produced by