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I’m beginning to understand this melt pool thing


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I have been reading everything I could find on heat distribution in candles and on wick testing. In wick testing they always say the melt pool should be ¼ to ½ inch deep, what they fail to say is that is at the edge of the melt pool. The thing that has been confusing me is that when I achieve a ¼ in melt pool at the edge in the middle my wax is melted to the bottom of my container, which is not a good thing. I use 6006 wax with no dye which becomes transparent when it melts, so I can clearly see the shape of the melt pool. I found a nice tech brief entitled “Multiphysics Analysis of a Burning Candle” that has an excellent graphic showing the surface temperature distribution of wax during burning, this helped me better understand what is happening in my candles. An ideal melt pool would be the same depth in the middle as at the edge, this is not achievable, but we should still try to get as close as possible. Your choice of container is going to have a significant impact on how close you can get to the ideal. My big mistake was, as a beginner, choosing short, wide tureen jars and metal tins. Short and wide is bad because most of the wax melts before the melt pool reaches the edge, your hot throw starts off good and then fades. Tins are bad because metal is an excellent conductor of heat, so you need a bigger wick to melt the wax at to edge. If you had a glass container that was the same size as your tin you would need a smaller wick, so your melt pool would not be as deep in the middle, making it closer to ideal. Glass is a good insulator, so it makes great candle containers, and the thicker the better. Using multiple wicks also helps you get closer to the ideal as you get a better heat distribution. I know I’m just a newbie here and most of you understand this stuff intuitively, but it is in my nature to try and understand the why of things. So now I think I’m going to order some nice status jars, then I shall put on my Don Quixote helmet and continue my quest to find the perfect wicks for my tureens.

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The overall proportions of your container make a difference too. Short squat containers can’t get as much air current moving quickly. Tins tend to get very, very hot toward the bottom.  You may initially think you need a bigger wick, but then that gets into big trouble as soon as the air current begins to flow.

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Well....as a newbie, that was very educational haha. But now you're making me question the jars I'm looking at. :huh:
https://www.fillmorecontainer.com/g16-03c-case12jar-12oz.html
 

Are these too wide? 

I'm also looking at doing 16oz Apothecary Jars, which are very wide, but I would be double or even triple-wicking them....so would that be okay? Wicking is the most complicated and confusing part about candle-making....

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6 minutes ago, LittleMissSunshine said:

 Wicking is the most complicated and confusing part about candle-making....

Amen to that! Others here could better help you with picking containers, but if you need to you can always double wick, or triple wick, mathematically speaking that will give you the best heat distribution, but I am not familiar with the disadvantages of using multiple wicks, but I'm sure there are some. Everything in candle making is a trade off.

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38 minutes ago, TallTayl said:

The overall proportions of your container make a difference too. Short squat containers can’t get as much air current moving quickly. Tins tend to get very, very hot toward the bottom.  You may initially think you need a bigger wick, but then that gets into big trouble as soon as the air current begins to flow.

I'm learning that, which is another reason to use straight sided glass containers. 

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24 minutes ago, LittleMissSunshine said:

Well....as a newbie, that was very educational haha. But now you're making me question the jars I'm looking at. :huh:
https://www.fillmorecontainer.com/g16-03c-case12jar-12oz.html
 

Are these too wide? 

I'm also looking at doing 16oz Apothecary Jars, which are very wide, but I would be double or even triple-wicking them....so would that be okay? Wicking is the most complicated and confusing part about candle-making....

 

I love the 16oz straight sided jars and use them myself occasionally. It is not necessary to double wick these jars. I single wick them and I have also single wicked larger apothecary jars successfully.

 

I have tried double wicking and the lessons I learned from that are not to double wick jars that don't need it. So any jar at 4" diameter or under I single wick. Double wicking I leave for the very large containers.

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Forgot to add that I once tried using wide, short, squat jars, sort of like tureen type at one time. I used them for a very short time before learning the hard way they don't make the best candle containers for a variety of reasons.

 

However, they do make excellent wickless candles. I would definitely pick a tureen jar to use if I were making wickless candles. They are perfect for that.

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55 minutes ago, Candybee said:

Forrest the National Candle Association website has all kinds of information on candles. Another good site to read up on wicks and how they perform is at Wicks Unlimited  http://www.wicksunlimited.com

Thanks, that is some useful information. I read one of the NCA's articles this morning, good stuff.

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