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CD vs CDN burn comparison in soy

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Heinz CD wicking is designed to perform well in viscous (thick) waxes, such as those composed of vegetable oil. Thus it's very popular for soy candles.

All wicking is treated with chemical salts so that it can wick fuel without being itself consumed in the flame. The chemical treatment is not a coating. It's soaked into the wick, so you can't see it. However, without this chemical treatment, no candle wick would work properly.

There is a special version of CD called CDN. Physically and visually, it's identical to CD. The only difference is that it's soaked with a different chemical solution to make it work properly in waxes that are acidic.

What we mean by an acidic wax is one that has a high percentage of free fatty acids. An example of free fatty acid is the stearic acid that some people use in small amounts as a wax additive. However, some waxes (such as palm wax) contain free fatty acids in large amounts.

German wicks such as CD and LX will not burn in such acidic waxes. The chemical treatments applied to those wicks are not sufficient to prevent them from being partially or mostly consumed in the flame. That's why Heinz offers a separate version of CD with a different chemical treatment.

Soy wax does not require the special chemical treatment because it isn't an acidic wax. The fatty acids in soy wax are bound up with glycerol to form triglycerides, which is just another name for oil. We can look, for instance, at the technical data sheet for C-3 container wax at http://www.elevance.com/docs/technical/13C2030CT_TDS.pdf. The free fatty acids are listed as a maximum of one-tenth of one percent. This amount simply represents an allowance for some possible decomposition of the oil that the wax is made of.

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Even though the chemical treatment of CDN is not required to burn soy wax, some people use that wick anyway. Both CD and CDN will burn in soy wax. The question is, how does the burn differ?

As a consequence of being more resistant to the acidity of the wax, specially-treated wicks such as CDN from Heinz and any wick from Wedo with the NST2 treatment (typically RRD or LX NST2) are also more resistant to the effects of the flame. Therefore, they don't tend to curl as much and don't as readily self-trim at the edge of the flame.

The photos below show two soy tumblers wicked with CDN 8 on the left and CD 8 on the right. From a distance, they look similar. The flame heights and the melt pools are about the same. Upon closer inspection, however, we see that the CD wick is curling and trimming properly. In contrast, the CDN wick has a more upright stance and is gradually accumulating unburned material at the tip.




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After 2 hours of burning, the CD candle has a better flame and melt pool than the CDN candle. The CDN wick is gradually accumulating more and more unburned material, the heat from which is beginning to make an oval melt pool.

One conclusion we can draw from this is that you should not automatically use CDN for soy containers in the belief that it is designed for this purpose. The technical considerations for wick selection favor CD for soy container waxes.

Another conclusion is that, if you consider using CDN, you should test it along with CD to see which works better in your application.

The third conclusion is my own personal one, which is that I would not bother to test CDN for soy candles at all. To me it is clear which wick is more suited to this application. I think the popularity of CDN for soy is based mainly on the spreading of incorrect information rather than on its actual performance.



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do you use the same size cd vs cdn ? I know you say they are identical in every way except the coating but does that coating make them burn hotter?

They are both size 8. It's not the coating but rather the soaking that's different. I don't think it intrinsically affects the burn rate or the flame temperature. When you first light the wicks, you can see an inherent similarity in performance. However, since the wicks react differently during the burn, the results can dramatically diverge in various ways.

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  • 2 weeks later...

Thanks for posting this. I tested endlessly with CDN and CD, with my GB464.. and time and time again I came back to the CD's, but my "candle guru" a friend back in Washington (who I respect very much but she was very stubborn) INSISTED the CDN's were better and what I "should" be using. In the end of course I went with what I know and I stuck with the CD's because its what performs for me... but I wasted alot of time testing to make her theory work, when I should have just trusted my results.

I had no idea about the soaking, I thought it was the coating that was the difference. I dont think I will ever be done learning!

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Thanks for posting this. I tested endlessly with CDN and CD, with my GB464.. and time and time again I came back to the CD's, but my "candle guru" a friend back in Washington (who I respect very much but she was very stubborn) INSISTED the CDN's were better and what I "should" be using.

That's the difference between making a wicking decision by testing versus by reading a website--you did it the right way. Tests like this are what we should be doing and sharing on the board to advance us. Not repeating what it says elsewhere or what was posted in the past. That just perpetuates misinformation or distorted information.

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I generally like CD's for my GB464 wax, but I tested an 8 oz square mason with NG Spiced Cranberry, (1 tsp pp CO, no dye), and the CDN 10 did better than a CD 10. There was less mushrooming. Wish I knew why. I'll be redoing the test with the 2 wicks side by side to compare, just to be certain it's not an anomaly.

Does anyone else find that sometimes the CDN's work better than the CD's? I'd rather use CD's because they are easier for me to get.


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Naomi- it could be with the heavier scents, the spices, and bakeries... that the CDN works better, because I dont use those scents generally (mostly spa types, fruits and florals) and CD works great. My one exception was Pumpkin Pie Spice... where the CDN did better. So maybe that has something to do with it? Let us know how your testing goes!

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