Why Candle Testing?

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I’m constantly burning candles all day long. Testers, all of them–I’m constantly looking for my next favorite scent or that right fragrance to capture the perfect moment. It can get a little bit… ridiculous. If you’re anything like me, you’ve probably got more than one candle going on right now, too. ^_^

Six testers on the coffee table… but there are 10 more on the dining table not pictured too!

First Burn

What do you prioritize when you test? For me, here’s what I’m looking for on my first burn:

  • scent throw: does it fill the room? I usually use soy wax (though I do make some coconut/paraffin candles) and I always wait 2 weeks minimum before I test, but if something doesn’t throw, I give it one more week and try it again… and then one more week and try the third (and last) time before I decide that it truly isn’t working out.
  • scent appeal: what are the fragrance notes? Does it appeal? Is it off-putting? Some people absolutely love Sea Salt and Orchid, but to me that is just way too cloying and it just doesn’t smell “real” to me. On the other hand, I could immerse myself in Midnight Jasmine all day, all night, in my dreams… mmm.

I don’t worry about the melt pool on the first burn. If I’m lucky I’ve got the right melt pool, but I almost never get the perfect melt pool on the first try.

(Almost. I just triple-wicked a candle that burns perfectly, and I’m currently trying it one size down to prove to myself that I have the right size. For the record, it’s IGI6046, triple wicked with LX16, burning Red Sangria from Candlescience. I’m trying LX14 right now and it’s not really succeeding… but you have to try before you know, right? ^_^) [ETA 2 hours later: … actually, by spacing the wicks out more, LX14 is doing beautifully. And this is why you test!]

Subsequent Testing

Now that I’ve decided if the fragrance works, it’s time to tune in the wick. (I’ve already figured out the vessel–I match that and the wax before anything else!) I pour a wickless tester and set it aside for two weeks (or longer, if the first burn tells me that this is one that has to cure a bit more.) Yup, wickless. Just wax and vessel.

After it’s cured, I use a metal skewer and stick holes where I want wicks to go, and then I cut off a piece of wick (1-2 inches) and insert it. A couple of my vessels are between 3-4 inches in diameter, and so I do this “biggest single wick possible” thing, then “smallest triple wicks possible”, and then I tweak from there–if the single-wick tunnels but the smallest triple wicks burn too fast or too hot, it’s going to be a double-wick.

I also weigh my candles upon every burn, and I try to make sure I burn the candles for at least 4 hours each time. Weighing the candles allows me to estimate burn time and lets me decide if the candle’s burning too fast (another indication of the wicks not being suitable). I have an ideal wax consumption rate for each vessel, and I’m trying to get as close to that ideal as I can.

Once the candle is:

  • full melt pool
  • ideal wax consumption rate
  • fantastic hot throw
  • burn time estimate is within target range

… now it’s time for the final test.

Customer Testing – The Final Frontier

I unashamedly use my best customers as candle testers. I’ll pour a candle, wicked, and ready for sale… and they will take it and use it as any person would. Some of them have pets, some of them have children, and they burn in all types of conditions. I ask them to let me know how long they burn it for and what it looks like.

If it never gets too hot, consistently achieves a full melt pool, and throws scent throughout their house… it’s ready for sale!

And that’s my method.

Estimating Wax Fill

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Without actually pouring wax into a container, how do you know how much wax it will hold? In short, this is how to do it (with details after the summary):

  1. Find out how much water (weight in ounces) the jar will contain when filled to the desired wax fill line.
  2. Find the specific gravity (or density) of your wax from the MSDS.
  3. Multiply the water weight by the specific gravity to get the wax weight.

Step 1: Find the water weight

First thing we need to do is figure out how much water weight will fill the vessel to the fill line. You can weigh your vessel empty, and then weigh it filled; the difference will be water weight. OR, if you have a scale with a tare function, place your vessel on the scale, tare to zero, and then pour water in until it reaches the wax fill level you would like.

The water weight to the fill line in the Shadowfire single-wick is 12.85 oz.

Step 2: Find the specific gravity of the wax

A reputable wax supplier will provide the MSDS for the waxes they sell. I use Ecosoya Q210 and I purchased my wax from Candlescience. On Candlescience’s website, I download the MSDS for my wax here.

Here’s the MSDS PDF on Candlescience’s product page.

In the MSDS, I look for mention of specific gravity or density… and yup, as I expected, here it is:

Candlescience’s MSDS for Ecosoya Q210 clearly lists the specific gravity in the physical and chemical properties section.

So now I know my specific gravity! I choose 0.89, the smaller number, because it’s always better to have too much wax than too little.

Step 3: Math!

In step 1, I found that my water weight is 12.85 oz. In step 2, I found that my specific gravity is 0.89. The math is super easy:

12.85 oz x 0.89 = 11.43 oz

I round that up to 11.5oz, and voilà: My wax (and FO) fill weight for the Shadowfire single wick vessel is 11.5 oz!

Estimating Candle Burn Time

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One question I occasionally get is, “How do I estimate how long my candle will last?” Here’s how!

Important Note

It is important to note that wax consumption will depend on the fragrance oil that is mixed in with the wax and also the wick’s capacity and number of wicks. This means that if you change fragrance, fragrance percentage, wax, or wick, you will need to re-test and recalculate your burn rate again. It’s easiest to do this during wick testing.

Step One: Gathering Data

During the wick testing phase, you’ll be testing for the ideal melt pool, hot throw, and vessel sturdiness. One more thing you can do while testing is record start and end candle weights.

  1. Weigh the candle: wick, wax, vessel, fragrance oils, decorations, and all. If your candle vessel has a lid, exclude it, don’t weigh it.
  2. When you start your test, record the starting weight and the time you light the candle.
  3. At the end of your test, blow out the candle. Weigh the candle again and record the ending weight and ending time.

Step Two: Calculations (with Example!)

The starting weight less the ending weight will give you the weight of the wax consumed during the burn. For example, I recently tested a candle that started the test at 498g and ended at 487g.

498g – 487g = 11g

We also need to figure out how long the candle burned. For example, the candle was lit at 10:15am and it was blown out at 12:10pm.

12:10pm – 10:15am = 1 hour and 55 minutes burn time

Now, take the weight of the wax consumed during the burn and divide it by the number of hours burned. (You can use minutes if you like.) This will give you a wax burn rate.

11g / 115 minutes = 0.096g/minute

To convert this to hours:

0.096g/minute x 60 minutes = 5.76g/hour

Step Three: Find Your Candle’s Burn Time

When you finally pour your candles, you should know how much wax is in each one. For the candle in our example, I decided that they would be 12.5oz each (not including vessel or wicks, but including wax and FO.) Since my burn rate is in grams, I’ll convert ounces to grams (it’s more accurate that way). Google makes it easy. 12.5oz is 354g.

Now I divide the weight of the wax (and fragrance oil) by my burn rate.

354g / 5.76 g/hr = 61.45 hours

Woot! We figured out that a 12.5 oz candle will probably burn for just under 61.5 hours. Since candles may burn faster or slower depending on where they are located (for example near a draft or in a still room) I like to couch the burn estimate in range, so I would then put the estimated burn time as 55 – 65 hours.

Priming/Waxing Raw Wicks

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Most candle supply stores sell pre-cut, primed, and tabbed wicks, and most of the time those will be all the wick you ever need. Sometimes, however, you need a really long wick for a tall container. Or you need a particular size but no one has it in stock or sells it.

You can buy spools of raw wicking (and tabs). I get mine from Candlewic (I don’t have any affiliation with them, but I use them as a supplier for my business too.)

Spools of raw wick
Spools of raw wicks purchased from Candlewic.

Raw wicks on spools will look a little different from what you are used to when you buy pre-tabbed wicks. The wicks don’t stand up on their own because there is no wax to stiffen them. Likewise, because raw wick is literally braided and woven cotton threads, these will have air bubbles that will either be trapped in the wick or will create bubbles around your wick when you use them.

soft spooled raw wick
On its own, raw wick is just cotton threads braided together. It isn’t stiff and doesn’t stand up by itself.

While I could work with raw wick directly, I prefer to pre-prime my wicks. For this, any type/color of wax will work! The only thing is to make sure the wax you use has a higher melting point. I use white beeswax because I make lip balm and I always have some beeswax lying around.

Beeswax in a cup
I melt beeswax in a cup for wick priming. I don’t bother cleaning out the cup because I plan on doing more in the future.

First I cut the wicks to the length I want. Right now I am still testing wicks, so I cut them pretty long (I’ll cut them into thirds after they’re primed). I then drop the wicks into the melted beeswax and stir them around until I’m sure they’re soaked through. Then I pull on some poly/plastic gloves to protect my hands.

Raw wick vs primed wick
Raw wick from the spool next to wick that I’ve cut and waxed. (Note the bit of beeswax I didn’t clean off.)

I fish out the wicks with a skewer or with tweezers, and then lay them on parchment paper or wax paper. I have a very small window in which I won’t burn my fingers (from hot beeswax) and I quickly straighten and smooth out the wicks by pulling them between my fingers and laying them out on the wax paper.

If I work too slowly the beeswax solidifies on me and leaves me with a tangled mess, but if that happens I drop the clump back into the melted beeswax in my cup and it all melts down again. (I should have taken pictures during this process but was too busy to do so. Next time, I’ll do it and put up a TikTok video!)

Waxed wick
This wick has been waxed (aka primed) and it is nice and stiff and stands on its own.

It doesn’t take long for my straightened wicks to be ready for me to pack them up for future use. I bought tabs and I have pliers–I will use some of these in candles and tab them as I wick the vessels.

Primed wicks
Raw wick from the spool next to wick that I’ve cut and waxed.

I am going to experiment with dying the beeswax in the future. Just imagine: red wicks in green wax for Christmas, purple wicks in pink wax for Valentine’s Day, or red-white-blue wicks in a triple wick candle for Independence Day. The possibilities are endless…

Burn Testing

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Most candlemakers ship their products with care cards or other such informational material that tell customers not to burn candles for more than 4 hours at a time, not to leave candles unattended, etc. Still, stories of cracked (or worse, exploding) jars abound. A chandler’s worst nightmare is hearing from a customer that their candle caused a fire.

Is there any way to protect against that? Proper wicking, of course… but most candles are tested under ideal conditions and following burn recommendations. And sometimes that slightly-larger wick is a bit too much for a vessel, but also throws amazingly and fills the room in an instant.

Less fragile materials (such as tin and concrete) are also popular. These materials have less of a tendency to crack or explode under extreme changes in heat, but they also just don’t have the same look that a glass jar does.

To help candlemakers decide if a vessel is safe or not, I abuse my vessels with over-wicked power burns and check to see how they hold up under intentional stresses beyond what a reasonable candlemaker would do. Here’s my latest power burn in the Marilyn vessel.

Notice how deep the melt pool is (1.5 inches–I measured). The outside of the thick vessel “only” reads 160F even though the inside is over 200F. The thickness of the vessel means that even under extreme burn conditions, this vessel will hold in all that hot wax and flame. Perfect if your customers like to burn their candles way beyond what their care cards say!