What Makes A Candle Soot?

Soot. Where does it come from?

Soot deposition has numerous sources. A homeowner's lifestyle and environment can help shed light on the increase in soot damage. For example, a household with smokers is at a higher risk for soot damage compared to a household with nonsmokers. Other common sources of soot deposition include fireplaces, stoves, furnaces, natural gas, oil, gas water heaters and candles.

It would be naïve to think that candle products made prior to the past five or ten years were not capable of causing smoke. Why are we now seeing a rise in claims of soot deposition? What has changed? The candle industry has more than doubled in the past five years, so it makes sense that we would see an increase in the number of soot cases since soot is a naturally occurring product. It is important to understand that soot has always existed, and always will. In fact, soot particles are what make a flame burn yellow. NASA has performed experiments in microgravity and experimented with the laminar soot processes. The experiments show that, in reduced gravity, the flame is round and not distorted as we see it on earth. Gravity elongates the flame cone and causes the flame to smoke given the right circumstances. The writer feels such circumstances include wick length and too much air circulation [drafts].

Another factor in soot deposition is consumer misuse

It seems that many consumers have lost the "art of burning candles". Any candle burned improperly may produce soot. For example, the longer the wick on a candle, the more soot it is likely to produce. Also, placing candles in rooms with drafts may increase soot deposition. Air circulation is needed to evenly distribute heating and cooling throughout the house. However, drafts produced by a ceiling fan or an open window will contribute to the possibility of soot emission from a burning candle.

Today's construction practices on new buildings may also contribute to ghosting stains. One possible explanation of this anomaly is the use of more synthetic materials than in the past. These materials may produce gases that, along with a driving force, cause soot to accumulate.

The impropriety of the poor having to live in houses with "poor air" over a century ago. The row houses of London had no ventilation and was warned of combusting materials without sufficient air. Those row houses were most likely very well ventilated by today's standards.

The air tightness of new construction is an issue of concern for indoor air quality professionals throughout the nation. Many studies today indicate that new homes have at best poor ventilation. Studies of newly built houses in Florida, North Carolina, Tennessee, and Washington indicated average air exchange rates of between .1 and .2 air changes per hour or only changing 10% to 20% of the air in the structure per hour. Few homeowners understand that to reduce energy costs homebuilders and designers greatly reduced the amount of fresh air permitted to enter the home. The American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) suggests .35 air changes per hour [or, 35 % of indoor air] to maintain adequate indoor air quality. London row houses would have been "windy" by this standard.


If we know the sources of soot, and we know some of the reasons why soot accumulates, then what can we do to minimize the effects of soot?

To prevent smoking, candle wicks should be trimmed to ¼" before lighting and re-trimmed to ¼" upon re-lighting.

If a candle begins to soot, take measures to ensure proper burning procedures are being done. Candles should never be power burned all day long! They should only be burned for 4 hours at a time. Keep in mind longer wicks and higher flames will produce more soot. As a consumer you should always follow the manufacturer's burning instructions for any candle.

Consumers need to make sure that rooms are properly ventilated and candles are kept out of drafts. Also, under no circumstances should a candle be burned while out of sight. Consumers must understand that the type of candle they purchase affects the amount of soot that is produced. For example, jar candles, among the most popular candles sold, may produce soot because of the inhibited airflow. As the wax burns further down into the jar, less fresh air can enter the container to efficiently burn the candle.

The most basic rule that consumers should follow is... if the candle appears to be emitting soot, do something about it.

Extinguish and allow the candle to cool, never move a lit or molten candle. Read and follow the manufacturer's burning instructions again. If necessary, trim and re-light. If the candle continues to smoke, discontinue its use and call the manufacturer.

The materials used to build new homes have changed rapidly with technology. With the expanded use of synthetic materials, it is believed that gases may be produced that contribute to soot emission. Most houses do not have ventilation systems. Fresh air should be accessible from outside of the structure and vents should direct "old air" out of the structure. The velocity of airflow should be controlled and systems must be fitted properly to each building.

Jazz Candles has taken serious steps to control the quality of our candles and to educate consumers. Take the time to read our warning labels and educate yourself on the proper way to burn a candle.