In oxyacetylene welding, the flame color sequence is described as which of the following?

In oxyacetylene welding, the flame color sequence is described as which of the following?

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

Answer: (C)

Flame color reflects the fuel-oxygen balance in oxyacetylene burning. When you first light the torch, acetylene is often burning with too little oxygen, producing a luminous orange flame from soot. As you open the oxygen further to reach a proper balance, the flame shifts to blue, indicating clean, efficient combustion suitable for welding. That’s why orange, then blue is the best description: you observe an initial orange flame during ignition, then it becomes blue as you adjust the mix. The other options don’t describe this transition you see in practice.

Flame color reflects the fuel-oxygen balance in oxyacetylene burning. When you first light the torch, acetylene is often burning with too little oxygen, producing a luminous orange flame from soot. As you open the oxygen further to reach a proper balance, the flame shifts to blue, indicating clean, efficient combustion suitable for welding. That’s why orange, then blue is the best description: you observe an initial orange flame during ignition, then it becomes blue as you adjust the mix. The other options don’t describe this transition you see in practice.