MAPP gas

A set of MAPP and oxygen cylinders used for oxy-fuel welding and cutting.

MAPP gas is liquefied petroleum gas 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 decomposes to explosive hydrogen and carbon, 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 liquid petroleum gas (i.e., propane-based) 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.

This gas is popular among glass lampworkers, for instance among glass bead makers.

Its biggest disadvantages are cost, being between two and four times more expensive than LPG (depending on quantity, supplier, and bottle size). While 9 kg LPG cylinder are common, the largest MAPP cylinder in Australia is 3 kg.

MAPP is colorless in both liquid and gas form. The gas has a pronounced garlic odor at concentrations above 100 ppm and is toxic if inhaled at high concentrations.

See [1].