MAPP gas
MAPP gas is liquefied petroleum gas (LPG) mixed with methylacetylene-propadiene. MAPP is the tradename for a product of the Dow Chemical Company. In Australia it is known as RazorGas and is a trademark of ELGAS.
The gas is used for welding due to its high combustion temperature of 2927 °C (5301 °F) in oxygen. Although acetylene has a higher welding temperature (3160 °C, 5720 °F), MAPP has the advantage that it requires neither dilution nor special container fillers during transport, allowing a greater volume of welding gas to be transported at the same given weight. Also, MAPP is advantageously used in underwater welding, which requires high gas pressures (under such pressures acetylene polymerizes explosively, making it dangerous to use).
The gas is also used for brazing and soldering, under combustion in ambient air, where it has considerable advantage over competing propane fuel due to its higher combustion temperature. A typical MAPP gas brazing operation would involve using it to silver braze (sometimes colloquially and inaccurately called silver solder) steel parts together.
Plumbers use both MAPP gas and propane for pipe soldering and brazing, but MAPP gas's higher combustion temperature makes such jobs quicker. MAPP gas is also popular among glass lampworkers, for instance glass bead makers.
The biggest disadvantage of MAPP gas is cost; it is between two and four times as expensive as propane (depending on quantity, supplier, and bottle size). While nine kilogram propane cylinders are common, the largest MAPP cylinder available in Australia is three kilograms. Additionally, MAPP gas torches often cost more than propane torches, around 3 times as much.
MAPP is colorless in both liquid and gas form. The gas has a pronounced garlic or fishy odor at concentrations above 100 ppm and is toxic if inhaled at high concentrations.