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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: 570 grams
- Candle Weight After: 556 grams
- Total Burn 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 = (570g – 556g) ÷ 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 570g, and the container weighed 120g, and we calculate our ROC as 3.5 grams/hour:
Wax Weight = 570g – 220g = 350g
Burn Life (hours) = 350g ÷ 3.5g/hr = 100 hours
These are extremely rough estimates 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.
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