FLAME TEMPERATURES

The temperature of a torch flame is determined by several factors:

• Is the fuel flow smooth or turbulent?
• Are the fuel and oxygen premixed, or diffused while burning?
• Where in a flame is the temperature measured?
• What is the temperature, humidity, pressure, present gas mixture, etc. of the air?
• What is the mixture of fuel vs. oxidizer?

An acetylene/oxygen flame may be neutral (equal mix: complete combustion, white rounded cone)

Carburizing (excess acetylene: large smoky yellow flame)

Oxidizing (excess oxygen: short, sharp inner cone, deeper purple hissing flame)

Sites discussing practical welding tend to report lower numbers than science-oriented sites because of the rapid heat loss that occurs in typical use.

Flame temperatures measured with thermocouples may be inaccurate.

As a general guideline consider these temperatures for a jeweler’s torch:

• 2237°F (1225°C) for Propane-Butane/Ambient Air
• 3992°F (2200°C) for Propane/Oxygen
• 4892°F (2700°C) for Acetylene/Oxygen
• 5300°F (2927°C) for MAPP Gas/Oxygen
• 5792°F (3200°C) for Hydrogen/Oxygen