Process for producing flat glass

A process for producing a flat glass, comprising:

• providing a glass melting furnace, a flat glass forming apparatus and at least one pair of tension rollers positioned between the glass melting furnace and the flat glass forming apparatus, the at least one pair of tension rollers including a roll base configured to contain a liquid therein;
• melting a glass in the glass melting furnace to form a molten glass;
• forming a glass ribbon by discharging the molten glass from the glass melting furnace to the tension rollers in a ribbon shape;
• introducing a steam film forming agent to the tension rollers in a liquid state, the steam film forming agent comprising a material being not gaseous at a temperature in the vicinity of room temperature and gaseous at a glass transition point of the glass or a temperature higher than the glass transition point;
• vaporizing the steam film forming agent to form a thin layer of a steam film on a surface of the tension rollers;
• stretching the glass ribbon by the tension rollers in an S-shape;
• rotating the tension rollers while applying a pressure to a face of the glass ribbon via the thin layer of the steam film such that the tension rollers polish the face of the glass ribbon;
• and
• forming the glass ribbon into a plate shape in the flat glass forming apparatus.