RATE CHART OF STABILO WICKS ( as an example )
What is Yield?
A candle wick is made up of many smaller cotton strands, sometimes with additional support threads made of cotton, paper, linen or even metal. All of these elements have weight and yield is a measure of this weight. All of these elements have weight and yield is a measure of this weight.
Wick Yield is simply the number of meters of raw (unwaxed) wick per kg.Let's take a look at two examples low:
Stabilo 4 = Yield = 1083 m/Kg (0.92 g/m) ,
Stabilo 14 = Yield =591 m/kg ( 1.69 g/m).
So, in the case of the Stabilo 4, if you took a 1kg spool of unwaxed wick and unwound it, it would be approximately 1083 metres long. If you did the same with the Stabilo 10 wick, it would only extend 591m/kg. So, a Stabilo 14 is roughly twice as heavy per metre as an Stabilo 4.
The smaller the yield, the more material there is in a meter of wick. A Stabilo 14 is therefore much heavier than a Stabilo 4. Although weight is not the only factor that influences how a wick will perform in a given blend, it is a pretty good indicator of power. It is particularly useful for comparing wicks from different families
The higher the yield, the smaller the wick and the flame and the resulting heat generated.
What is ROC – Rate of consumption
The rate of wax consumption in grams by the wick in one hour. The higher the burn rate the more wax which is being consumed. Used to determine how well a wick and wax combination is performing
If you divide the difference in weight by the time your candle burned, you can calculate how fast your candle is burning through the wax. Let’s look at an example:
You’re safety testing a container candle, and measure the weight before and after burning it for 4 hours, including the container weight.
Candle Weight Before: 600 grams
Candle Weight After: 586 grams
One Cycle Burning Time: 4 hours
You can calculate the Rate of Consumption (ROC) of the candle system with this equation:
ROC = (Candle Weight Before – Candle Weight After) ÷ Burn Time
In our example:
ROC = (600g – 586g) ÷ 4hr = 3.5 grams/hour
Technically, you could use this to estimate the entire burn life of the candle, but most container candles burn hotter further down in the container, with a higher ROC. But if you’re trying to find a rough estimate, you can calculate the burn life of a design if you know the wax weight in the container.
Wax Weight = Total Candle Weight – Container Weight
Burn Life (hours) = Wax Weight ÷ ROC
If our total candle started as 600g, and the container weighed 120g, and we calculate our ROC as 3.5 grams/hour:
Wax Weight = 600g – 220g = 380g
Burn Life (hours) = 380g ÷ 3.5g/hr = 108 hours
These are only estimate values for the reason mentioned earlier, but the theory holds up. The best way to figure out your candle life is to burn through the entire candle, 4 hours at a time, and tracking how many hours it burns for.
Most candles will burn for a range depending on the burn habits of the users, but a 4-hour standard test from start to finish will supply you with an approximate estimate.
Let’s look at a real example of one tested candle we did and charted the ROC here
( technically and theoretically you should do 4 hours burn cycles , in the attached test we simulate different hours as a final users normally would do )
How High Should A Candle Flame Be?
It really depends on the candle, but a properly functioning candle wick should leave a melt pool (that is the area around the wick) that grows by 0,64 cm in depth for every hour that the candle is burning.
To get to this, you need a wick that delivers a flame that is between 1.27 a 5 cm in height. If the candle is fairly small, it should be closer to 1.27 and if it’s huge then 5 cm is the best bet.
It’s also worth noting that the material that a candle is made from will influence the height of a flame and beeswax as well as soy waxes and vegetable waxes need a more bigger wick than a standard paraffin wax candle does.
You can easily experiment with wick lengths to find the right length for your candle, and it’s best to leave it slightly too long than to trim it way too short.
What about the Pool Diameter ?
When you light a candle, the heat of the flame melts the wax near the wick. This liquid wax is then drawn up the wick by capillary action.The melted wax is your pool. The pool releases the trapped fragrance in the air. A properly sized wick is expected to melt wax at a specific rate to provide optimal scent performance (hot throw).
In more detail : The mixture of fuel and oxygen occurs by convection and diffusion: The liquid fuel rises by capillary forces in the wick. Here it evaporates due to the high flame temperature. The hot gas rises and mixes with the ambient air through diffusion. In addition, colder air flows into the lower part of the flame through convection. Here it also mixes with the gaseous fuel. The actual combustion reaction preferably starts in a zone of the flame above the wick.
The heat of the flame vaporizes the liquid wax (turns it into a hot gas), and starts to break down the hydrocarbons into molecules of hydrogen and carbon. These vaporized molecules are drawn up into the flame, where they react with oxygen from the air to create heat light, water vapor (H2O) and carbon dioxide (CO2).