Inside a Flame

Light a candle. Watch the flame stand still in the still air. It looks like a single, simple thing — a tongue of yellow light, dancing. But it is not one thing. It is three zones, each with its own chemistry, its own temperature, its own relationship to fire. Start at the base. Where the flame meets the wick, there is a pale blue ring — the hottest part of the flame, around fourteen hundred degrees Celsius. Here, wax vapor and oxygen meet in nearly perfect proportion. Combustion is complete. Almost nothing escapes unburned. The blue color comes from excited carbon molecules, from CH radicals briefly flaring as they react. This is the engine room. Just above the wick, inside that blue ring, there is a dark zone — a shadow at the center of fire. Unburned vapor rises from the wick, not yet hot enough to ignite. A cold core inside a hot shell. The flame feeds from its own interior, drawing vapor upward before consuming it.