A burning candle might look simple to the naked eye but there is a lot of chemistry and physics behind it. In the 1800s several lectures were given on the scientific principles that led to candle burning, all of which were possible only by observing it for a long time.
Today, the thought of observing a burning candle might seem ridiculous but a lot of people still don’t know exactly what happens when you burn a candle.
“When candles burn, where does the candle wax go?” might be something you wondered yourself. The short answer to that is that it turns into a hot gas through vaporization. However, there are a lot of other things that go on too.
Let’s take a look into how candles burn to better understand where and why the wax disappears.
When Candles Burn, Where Does the Candle Wax Go?
When a candle burns, the wax is melted and travels up the wick through capillary action. When the wax reaches the flame it is vaporized. This results in a gas being released into the air. The gas released will depend on the type of wax melted.
Before we explain this in more detail, it is important to know what wax is. Only by knowing its composition will you be able to better understand how it disappears from a burning candle.
Wax is quite similar to plastic in many ways as it is made out of a variety of different substances. Many different chemicals are combined to form the wax that we know and use in candles. The main purpose of wax in a candle is to keep the candle lit by feeding itself slowly to the flame.
No matter what type of candle it is, i.e. whether it is a paraffin wax one or an all-natural one, the principle remains the same. The only difference is the output, which is the type of gas it produces when burnt.
Paraffin wax is essentially long-chained hydrocarbons that react with oxygen and produces carbon monoxide as a result. The carbon monoxide then reacts with oxygen again to form carbon dioxide. This is why you see a blue flame at the bottom and not a fully yellow flame.
When you light up a candle, the heat causes the wax near the wick to melt. The liquid wax is then drawn up due to capillary action, which is the ability of a liquid to flow in narrow spaces without gravity or external forces. A good example of this is how trees pull water up through branching.
Once the liquid wax is drawn up the wick, the heat from the flame turns the liquid wax into a hot gas through vaporization. The hydrocarbons in the wax are broken down into hydrogen and carbon molecules, which then react with oxygen from the surrounding air to not only produce heat and light but also water vapor and carbon dioxide. The resulting heat then melts more wax near the wick and the cycle continues until there is no more wax left.
For an efficient burn, the candle must have clean combustion. Otherwise, you will see the flame flickering and producing soot. In the case of unstable combustion, it takes a little bit of time to stabilize. If it doesn’t, you might have to put the candle out and light it again.
Put simply, the wax from a burning candle turns into a gas and goes into the air. You can’t see it as it’s invisible just like most gases. For example, air, water vapor, and oxygen are all gases you can’t see. That’s why many people ask where wax goes when a candle burns because it almost seems like it just disappears.