Temperatures

Torch Fuel Characteristics and Temperatures
Chemical Fuel Formula Special Characteristics Flame Temp. w/Oxygen Flame Temp. w/Air BTU per lb.
Acetylene C2H2 Burns hottest; popular fuel gas; not recommended for use with platinum 6300°F 4217°F 21,499
Natural Gas ** Burns clean; economical to use 4600°F 3420°F —
Propane C3H8 Burns clean; economical to use 4780°F 3497°F 21,260
Butane C4H10 Low heat; available in portable containers 4995°F 3443°F 21,298
Hydrogen H2 High heat; cleaner than acetylene 4850°F 3713°F 61,085
MAPP® C3H4 Somewhat concentrated high-temperature flame 5300°F 3600°F 2300

** Typical analysis: methane 83.4%, ethane 15.8%, nitrogen 0.8%.

High Temperature Judged By Color
°F °C Color
752 400 Red heat, visible in dark
885 474 Red heat, visible in twilight
975 525 Red heat, visible in daylight
1077 581 Red heat, visible in sunlight
1292 700 Dark red
1472 800 Dull cherry red
1652 900 Cherry red
1832 1000 Bright cherry red
2012 1100 Orange-red
2192 1200 Orange-yellow
2372 1300 Yellow-white
2552 1400 White welding heat
2732 1500 Brilliant white
2912 1600 Dazzling white, blue-white

Annealing Temperature Guide

Time at the full annealing temperature will depend on the thickness of the section, but 1 minute per mm of section should be sufficient for thickness up to about 5 mm. Too frequent annealing or annealing for too long can cause grain growth which may make subsequent working or polishing to a smooth surface more difficult.

Specific Gravity and Metal Melting Points
Metal Melting Point °C Melting Point °F Specific Metal Melting Point
°C		 Melting Point°F Specific
Aluminum 660 1220 2.7 Iridium 2454 4450 22.5
Bronze 1060 1945 8.8 Iron 1535 2793 7.9
Copper 1083 1981 8.9 Lead 327 621 11.3
Gold (fine) 1063 1945 19.3 Nickel 1455 2651 8.8
22K Yellow 977 1790 17.3 Nickel Silver 1110 2030 8.8
22K Coin 940 1724 17.2 Palladium 1549 2820 12.2
18K Yellow 1030 1885 15.5 Platinum (Pure) 1774 3225 21.4
18K Green 966 1770 15.6 5% Cobalt 1765 3209 20.8
18K Rose 932 1710 15.5 5% Iridium 1790 3254 21.4
18K White 940 1725 15.7 10% Iridium 1800 3272 21.5
14K Yellow 960 1760 13.4 5% Ruthenium 1795 3263 20.7
14K Green 835 1535 13.6 Silver (Fine) 961 1762 10.6
14K Rose 827 1520 13.4 Sterling 920 1640 10.4
14K White 975 1785 13.7 Stainless Steel 1371 2500 7.8
10K Yellow 980 1796 11.6 Titanium 1800 3272 4.5