Candle Science

Candle science refers to the scientific study and understanding of candles, including their composition, properties, and the science behind their behavior. It involves understanding the materials used to make candles, such as wax, wicks, and additives, as well as the various factors that affect their burning characteristics, such as temperature, airflow, and fragrance.

Here are some key aspects of candle science:

  1. Wax: Candles are typically made from different types of wax, including paraffin wax, soy wax, beeswax, and palm wax. Each type of wax has its own melting point, burn rate, and scent throw, which can impact the overall performance of the candle.
  2. Wicks: The wick is the part of the candle that ignites and sustains the flame. It is usually made of cotton or a cotton blend, and its size, thickness, and composition can affect the way the candle burns. The wick’s length and placement within the candle also play a role in controlling the size and stability of the flame.
  3. Additives: Candle manufacturers often use additives to enhance the performance and aesthetics of candles. These additives can include colorants, fragrances, and stabilizers. Understanding the chemistry of these additives helps in creating candles with desired characteristics, such as color, scent, and burn time.
  4. Combustion: When a candle burns, it undergoes a chemical reaction called combustion. The heat from the flame melts the wax near the wick, vaporizing it and supplying fuel to sustain the flame. The vaporized wax reacts with oxygen from the air, producing carbon dioxide, water vapor, and releasing energy in the form of heat and light.
  5. Candle Behavior: Factors like the diameter of the candle, ambient temperature, and airflow affect the way a candle burns. For example, a larger diameter candle may require a thicker wick to ensure complete burning, while a drafty environment can cause uneven burning or flickering.

Understanding candle science can help candle makers create safer and more efficient candles. It also enables them to experiment with different waxes, wicks, and additives to achieve desired burn times, scent throw, and visual aesthetics. Additionally, candle science is important for ensuring candle safety by studying flame behavior, potential hazards, and proper handling techniques.


Candles burn through a process known as combustion. When a candle is lit, the heat of the flame melts the wax near the wick. This liquid wax is then drawn up the wick, which acts as a fuel delivery system, through a process called capillary action. As the liquid wax reaches the top of the wick, it vaporizes and reacts with oxygen in the air.

The heat of the flame provides the activation energy needed to initiate the chemical reaction between the vaporized wax and oxygen. This reaction produces heat, light, water vapor, carbon dioxide, and other byproducts. The heat from the flame then sustains the combustion process by continuously melting and vaporizing more wax.

The shape and size of the flame can provide insights into the efficiency of the combustion process. A well-formed flame typically has three regions: the dark cone at the base, the bright inner cone, and the faint outer cone. The dark cone is where the vaporized fuel is drawn up the wick and reacts with the oxygen. The inner cone is the hottest part of the flame, where complete combustion occurs. The outer cone is where the combustion is incomplete, and soot particles are formed.

To keep a candle burning, it requires a continuous supply of fuel in the form of melted wax, a source of heat to initiate the reaction, and an adequate oxygen supply. If any of these elements are limited, the flame may flicker, produce excessive smoke or soot, or eventually extinguish.


A candle flame typically exhibits several different colors, each representing different temperature ranges and chemical reactions occurring within the flame. The colors can vary depending on factors such as the type of fuel being burned and the presence of impurities.

  1. Blue: At the base of the candle flame, closest to the wick, you may observe a blue color. This region of the flame is the hottest, reaching temperatures of around 1,400 to 1,600 degrees Celsius (2,500 to 2,900 degrees Fahrenheit). The blue color is an indicator of complete combustion, where hydrocarbon molecules in the wax vaporize and react with oxygen in the air to produce carbon dioxide and water vapor.
  2. Yellow: Above the blue region, you will usually see a yellow color. This part of the flame is slightly cooler than the blue region, ranging from approximately 800 to 1,400 degrees Celsius (1,500 to 2,500 degrees Fahrenheit). The yellow color is caused by incandescent soot particles produced by incomplete combustion. These particles are heated to the point of glowing, emitting yellow light.
  3. Orange/Red: The outermost part of the candle flame appears orange or reddish. This region has the lowest temperature, generally ranging from 600 to 800 degrees Celsius (1,100 to 1,500 degrees Fahrenheit). The orange/red color is a result of further cooling and incomplete combustion of the soot particles, which emit less light due to lower temperatures.

It’s important to note that the specific colors and their distribution can vary depending on factors such as air flow, draft, and the presence of contaminants in the fuel or environment. Additionally, colored candles or candles with additives can introduce additional hues to the flame.


A candle flame typically points upward due to a combination of factors related to the physics of heat, convection, and gravity. Here’s a simplified explanation:

  1. Combustion and heat: A candle flame is produced through the combustion of wax vapor or liquid fuel. Combustion is an exothermic process that releases heat and light energy. The heat generated by the flame causes the nearby air molecules to become hot.
  2. Expansion and upward movement: When air is heated, it expands and becomes less dense than the surrounding cooler air. As a result, the hot air rises due to buoyancy or convection. The upward movement of hot air creates a flow pattern known as a convection current.
  3. Oxygen supply: The flame requires a continuous supply of oxygen for combustion. The hot air rising around the flame creates a draft or updraft, drawing in fresh air from the bottom. This airflow replenishes the oxygen needed for the flame to sustain itself.
  4. Gravitational force: Gravity also plays a role in the flame’s upward direction. Hot air rises because it is lighter or less dense than the colder air around it. However, gravity acts as a force that tends to pull everything downward. The combination of the upward convection current and the downward force of gravity results in the flame pointing upward.

It’s important to note that the shape and direction of a candle flame can be influenced by various factors such as drafts, air currents, and nearby objects. However, the basic principle of hot air rising due to convection and the need for oxygen supply remain the primary reasons why a candle flame typically points upward.