Monthly Archives: February 2013

Feb
02

Science of Candle Wicks

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Candle Wicking Class

One of the most important components of a candle is the wick. The wick is the fuel (candle wax vapor) delivery system to the flame that allows a candle to burn. Before we explain how candle wicks burn, we will share with you the history of candle wicking. We will finish this class by helping you choose the correct wick for your candles.

History of candle wicks: Egyptians made a form of candle wick by taking fibrous reeds, called rushes, dipping them in animal fat, and lighting them. Since these rushes were fibrous in nature, they allowed the fat to be absorbed by the plant and provided the fuel that the flame needed to keep the “rushlight” lit. Years later, the Romans created an improved wicking system by loosely weaving fibers together. This provided for longer burn time, with the function of the wicking remaining the same.

Modern-day wicks are tightly woven or braided threads of cotton or other fabric material; sometimes including a core (cotton, paper, zinc). The woven material of the wick is then treated with a chemical solution to make them flame retardant. This process is called “mordanting”. Wicks are made fire retardant so that the fuel (the wax) travels up the wick, forms a vapor fuel and the fuel is burned. If the wicks were not made fire retardant, the wicks would burn themselves out before the wax of the candle could be used as fuel. Some candle wicks include a core that the threads are woven around; providing the wick with the ability to stand up. By the way, candle wicks made in the US do not contain lead. Lead core wicks were banned in the US back in 2003.

Before wicks are used, they typically undergo a process called “priming”. Priming involves dipping the wicking into wax. You see, when the threads of a wick are woven, there can remain very tiny air pockets within the threads of the wick. Priming simply fills in those air pockets. It is important to understand that a candle wick is considered primed after being in contact with melted wax for approximately 5 minutes (which is long enough for the air pockets to escape). There is no need to coat a wick with massive amounts of wax when priming. The fuel of the candle actually comes from the candle wax of the candle traveling up the wick to the flame, not from the wax used during priming. Candle wicks are assembled using machinery, so there will be times when wicks will have more priming wax on them, and times when they have less wax on them. This extra wax, or lack of does not affect the performance of the wick burn. It is the woven fibers of the wick that determine proper burn time.

Once wicks undergo priming, they are then “tabbed”. This involves placing one end of the wick into the hole of a metal wick sustainer tab and then crimping the tab of the wick sustainer. This attaches the wick tab to the wick. Wick sustainer tabs allow wicks to stand up in candles. Wick sustainer tabs typically come in the following sizes: 20mm, 15mm, and 30mm self-centering. The size of the wick sustainer tab refers to the diameter of the wick tab.

The neck size of the wick tab, which typically is 3mm, 6mm, or 10mm in height, controls how far down the candle will burn; extinguishing the wick before it hits the very bottom of the candle. This helps prevent candle glass from getting too hot and potentially breaking.

Size matters: When choosing the proper size of wick for your candle, please understand that as the “number” on the wick size goes up, so does the area it is capable of melting when burning. Example: A CD-10 wick will burn a smaller diameter than a CD-12. A zinc core 44-24-18z will burn a smaller diameter than a zinc 51-32-18z wick.

Using the proper size wick is very important! In the event that you use too small of a wick, your candle wax will not burn all the way across your candle, and you may not have sufficient scent throw. If you use too large of a wick, your candle will burn too fast, and you will have increased “mushrooming ” (carbon build up) on your wick.

What is the science behind a burning candle? A burning candle is an example of a chemical reaction between three major elements: oxygen, hydrogen, and carbon. The wax in a candle is composed of atoms of hydrogen and carbon. When the wick is lit, wax begins to melt, and the carbon and hydrogen atoms move up the wick to react with the oxygen atoms in the flame. Actually, the flame you see on a candle is proof of a chemical reaction of carbon and hydrogen atoms with oxygen. The heat from the wick causes the carbon and hydrogen atoms to break apart, and combine with oxygen to form a gas. This is called pyrolysis. You will notice that the flame of a candle is different colors. The blue part of the flame is the hottest part of the flame. The flame is blue because of sufficient oxygen being provided in the reaction. What happens when there is not enough oxygen available to complete the reaction? You will have an excessive number of carbon atoms that group together to form soot. Since soot is black in color, it easily absorbs heat; and this heat allows them to glow. It is these carbon molecules that create the yellow, orange, and red colored portion of the flame. When soot particles glow because they are hot it is called incandescence. Ultimately, a burning candle gives off water vapor, and carbon dioxide (the very same gas we exhale when we breathe).

Over the past decade, there has been a steady climb in the sales of soy wax candles; claims being made that soy wax candles are somehow “better” for you than paraffin candles. Putting aside all bias and focusing on science alone will allow us to make the following conclusions: 1. All waxes are primarily hydrocarbons, whether the wax is of animal, vegetable, or petroleum origin. The chemical composition of all waxes used for candle-making is similar. 2. All waxes produce a yellow flame due to the presence of carbon. 3. No specific type of wax or wax blend is considered “best” for candlemaking. All candle waxes, when provided in high-quality format,  have been shown to burn cleanly and safely. 4. No candle wax has ever been shown to be toxic or harmful to human health. 5. There is no such thing as a soot-free wax. All organic compounds when burned will emit some carbon (soot) due to incomplete combustion. (http://www.candles.org/elements_wax.html). In fact, we all experience small levels of carbon in our air everyday simply by cooking our food. It would be ridiculous to tell people to stop cooking their food to avoid carbon in the air. How about carbon dioxide- the air we all exhale? Should we all stop breathing to prevent putting this carbon in the air? It is time for science and common sense to unite!

The science behind a burning candle is important to understand because for a wick to perform effectively, it is reliant on other components of the candle. Some fuel sources will easily travel up the wick and produce the fuel vapor needed to keep the wick burning (refined paraffin wax is a good fuel source). Other waxes, such as soy wax, will require a larger wick to allow for pyrolysis to occur. That is why at Natures Garden, we suggest that candle makers “wick-up” when making vegetable wax candles.

Other candle components that affect the efficiency of the burning wick are fragrance and coloring. Fragrances are composed of a combination of essential oils, resins, and other aromatic chemicals (ketones and aldehydes). Some of these fragrance ingredients will easily travel up the wick and react with the oxygen, others do not travel up the wick as easily. Each component of a fragrance oil has individual flash points (the temperature at which its vapor will combust). When a fragrance oil contains higher levels of heavy base notes, such as musk, vanilla, amber, the candle may require a larger wick to allow for pyrolysis to occur. Lighter, lower flash point fragrance components will easily travel up the wick and burn. Special care should be taken when using citrus type fragrances that have a low flash point. If the wick size is too big, it may cause the citrus fragrance to give off a petroleum aroma instead of a citrus aroma. Using too big of a wick with low flash point citrus fragrances can also create a fire hazard; causing the entire top of the candle to ignite.

Coloring can also affect candle wicking. Candles require the use of dyes specifically formulated for candle making. Any coloring that contains water or glycerin will not work in candles. Color pigments, mica pigments, and titanium dioxide do not work well in the interior of candles. These pigments clog the candle wick; causing increased smoking and potentially causing your candle wick to stop burning. If these types of pigments are used during candle making, they are used only for coloring the outside of the candle by dipping the candle. Crayons are an example of color pigments suspended in a wax medium. It is never a good idea to color your candles with crayons as suggested by some media sources.
Choosing your candle wicking:

There are literally hundreds of types of wicks you may choose for wicking your candles. Most of the wicks on the market are made from braided or knitted fibers that allow for a slow, consistent burning candle. Candle wicks are typically one of the following types of wicks (provided by the national candle association) :

Flat Wicks. These flat-plaited or knitted wicks, usually made from three bundles of fiber, are very consistent in their burning and curl in the flame for a self-trimming effect. They are the most commonly used wicks, and can be broadly found in taper and pillar candles.

Square Wicks. These braided or knitted wicks also curl in the flame, but are more rounded and a bit more robust than flat wicks. They are preferred for beeswax applications and can help inhibit clogging of the wick, which can occur with certain types of pigments or fragrances. Square wicks are most frequently used in taper and pillar applications.

Cored Wicks. These braided or knitted wicks use a core material to keep the wick straight or upright while burning. The wicks have a round cross section, and the use of different core materials provides a range of stiffness effects. The most common core materials for wicks are cotton, paper, zinc or tin. Cored wicks can be found in jar candles, pillars, votives and devotional lights.

At Natures Garden, we offer several varieties of wicks based on our own successful testing.

HTP wicks- These wicks are created with a flat braided cotton fiber design, but also have paper fibers contained with the braid. These wicks provide a cleaner burn, controlled curling, and self trimming capabilities. Typically used when a hotter burn is necessary. Used with all types of waxes.

Zinc Core Wicks- These wicks are made with a cotton fiber braid, surrounded by a zinc core. Zinc wicks are known for allowing wicks to stand up in applications, and are thus frequently used in container candles. In the event that you are using vegetable waxes for your candles, you will want to “wick up” on the size of your zinc core wicks, as they do not burn as hot as other varieties of wicks.

CD Wicks- These wicks are a flat braid wick composed of cotton with special paper woven around them. These wicks provide excellent capillary action. CD wicks provide a hot burning wick and provide for significant rigidity. These are our favorite types of wicks here at Natures Garden. Used with all types of waxes.

Hemp Wicks- These braided wicks are made with natural fibers of hemp instead of cotton. Hemp wicks provide for a hotter burning wick and increased rigidity. Used with all types of waxes.

Wooden Wicks: Composed of wood, these wicks provide 100% rigidity in candles. These wicks do not require any type of trimming, produce no mushrooms, and allow for a fast melt pool.

To help you choose the best type/size wick for your candle applications, please visit our wicking chart. We provide this chart simply as a guide. It is not meant to be a substitute for your own testing. Testing is your responsibility.

In addition, Natures Garden offers sample packs of our wicks for you to try prior to committing to larger-sized packs of wicks.

Deborah Ward

CEO Natures Garden

Natures Garden Candle Wicks

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