Why Welding Arcs Glow Different Colors
Welding arc color depends on shielding gas: argon produces blue (gas ionization), broader gases produce white. Same physics as neon signs. All arcs produce damaging UV regardless of visible color.
Welding arcs aren't always bright white — the color depends on the welding process, shielding gas, and base metal. Blue arc: Typically seen in TIG (GTAW) welding, especially when welding aluminum or stainless steel with argon shielding gas. The blue comes from argon gas ionization — excited argon atoms emit photons in the blue-violet spectrum. Bright white arc: Common in stick (SMAW) welding and MIG welding, where the flux or different shielding gases produce a broader spectrum of light. Green tint: Can appear when welding copper alloys. The physics: An electric arc ionizes gas molecules, creating plasma. As electrons in the ionized gas drop back to lower energy states, they emit photons at wavelengths characteristic of that element — the same principle behind neon signs (neon = red-orange, argon = blue-violet). Regardless of visible color, ALL welding arcs produce intense ultraviolet radiation that can cause arc eye (photokeratitis) even if the visible light seems gentle. The UV output is not correlated with visible brightness or color.