In oxyacetylene welding, what color is the flame?

In oxyacetylene welding, what color is the flame?

• A. Blue
• B. Green
• C. Orange
• D. Orange, then blue

Answer: (D)

The color of an oxyacetylene flame tells you how balanced the fuel (acetylene) and oxygen are burning. When you first light the torch, you often see a bright orange, sooty flame because there isn’t enough oxygen yet to burn the fuel cleanly. As you adjust the gas valves toward a neutral balance, more oxygen is supplied and the flame cleans up, turning blue. The blue portion indicates more complete combustion, hotter and cleaner burning, which is what you want for welding. So the observed sequence—orange initially, then blue—reflects moving from a fuel-rich flame to a properly balanced neutral flame, which is why that choice is the best answer.

The color of an oxyacetylene flame tells you how balanced the fuel (acetylene) and oxygen are burning. When you first light the torch, you often see a bright orange, sooty flame because there isn’t enough oxygen yet to burn the fuel cleanly. As you adjust the gas valves toward a neutral balance, more oxygen is supplied and the flame cleans up, turning blue. The blue portion indicates more complete combustion, hotter and cleaner burning, which is what you want for welding. So the observed sequence—orange initially, then blue—reflects moving from a fuel-rich flame to a properly balanced neutral flame, which is why that choice is the best answer.