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.