air) are not considered oxy-fuel torches and can typically be identified by a single tank (oxy-fuel cutting requires two isolated supplies, fuel and oxygen). Most metals cannot be melted with a single-tank torch. Consequently, single-tank torches are typically suitable for soldering and brazing but not for welding. Uses Oxy-fuel torches are or have been used for: Heating metal: in automotive and other industries for the purposes of loosening seized fasteners. Neutral flame is used for joining and cutting of all ferrous and non-ferrous metals except brass. Depositing metal to build up a surface, as in hardfacing. Also, oxy-hydrogen flames are used: in stone working for "flaming" where the stone is heated and a top layer crackles and breaks. A steel circular brush is attached to an angle grinder and used to remove the first layer leaving behind a bumpy surface similar to hammered bronze. in the glass industry for "fire polishing". in jewelry production for "water welding" using a water torch (an oxyhydrogen torch whose gas supply is generated immediately by electrolysis of water). in automotive repair, removing a seized bolt. formerly, to heat lumps of quicklime to obtain a bright white light called limelight, in theatres or optical ("magic") lanterns. formerly, in platinum works, as platinum is fusible only in the oxyhydrogen flame and in an electric furnace. In short, oxy-fuel equipment is quite versatile, not only because it is preferred for some sorts of iron or steel welding but also because it lends itself to brazing, braze-welding, metal heating (for annealing or tempering, bending or forming), rust, or scale removal, the loosening of corroded nuts and bolts, and is a ubiquitous means of cutting ferrous metals. Apparatus The apparatus used in gas welding consists basically of an oxygen source and a fuel gas source (usually contained in cylinders), two pressure regulators and two flexible hoses (one for each cylinder), and a torch. This sort of torch can also be used for soldering and brazing. The cylinders are often carried in a special wheeled trolley. There have been examples of oxyhydrogen cutting sets with small (scuba-sized) gas cylinders worn on the user's back in a backpack harness, for rescue work and similar. There are also examples of both non-pressurized and pressurized liquid fuel cutting torches, usually using gasoline (petrol). These are used for their increased cutting power over gaseous fuel systems and also greater portability compared to systems requiring