[schmidling]

Candle wick chemistry

According to net wisdom, treating a cotton yarn with borax and salt will improve the burning characteristics of the yarn and make a very fine candle wick.

The yarn is soaked in a solution of 4 tbs borax, 2 tbs salt and 1.5 cups of water.

The soak time varies from 15 mins to 48 hrs depending on Moon phases or something but I can find no consensus on the time.  It is a saturated solution and I can think of no reason why it would take more that 15 mins to saturate the yarn.  This is for a yard weight of about .5 gram per yard and a one yard piece for testing purposes.

After soaking, it is dried for 8 to 48 hrs, again depending on the Moon.

Seems to me you could dry it in about 10 mins in a toaster oven at about 200F.  Weighing the sample before soaking and after drying confirms this.

The final step is to soak the dried sample in melted wax and then cool it to room temp.

I have done all this several times and compared the burning characteristics in both candles and the wick alone and find if anything, the untreated works better.

I see no difference when comparing just burning a short piece of wick but when used in a candle, the untreated one seems to burn longer and better.

What is the chemistry going on here and does it make any sense or just another internet fake news?

Thanks,

Jack

[billnotgatez]

maybe they were just talking about flame color?

Red
Strontium chloride or strontium nitrate

Orange
Calcium chloride

Yellow-green
Barium chloride

Orange-yellow
Sodium chloride (table salt) or (street lights)

Apple green
Borax (sodium borate)

Green
Copper(II) sulfate, boric acid

Blue
Copper(I) chloride, butane

Violet
3 parts potassium sulfate, 1 part potassium nitrate (saltpeter)Blue/light violetPotassium chloride

[billnotgatez]

Homemade Flame Retardant

https://www.instructables.com/Homemade-Flame-retardant/#:~:text=This%20works%20because%20the%20borax,to%20char%20instead%20of%20burn.

This works because the borax forms a primitive form of glass as it is exposed to the heat of the flame. The glass acts as an insulator, protecting the paper fibers from the heat and allowing them to char instead of burn. The char acts as an additional insulator. Eventually there is not enough heat to support combustion and the fire goes out.

I am not sure this would  be a factor for improving candle wicks.
Seems at this point your experiments would prove different.

[Borek]

I was always under impression that borax treated wicks don't have tendency to grow too long when the candle burns, so they don't need to be cut away.

[schmidling]

Thanks for the thoughts.  That link was interesting but I can make no sense of his pictures.
The two are identical.   The glassification seems to explain the phenomenon.

Turns out my problem seems to have been in the yarn I was using.  When I tried using a plain white cotton, it had quite an impact but if what he says is true, it should not work at all for a candle wick.

Using the plain cotton, and with the same amount of wick above the wax, the treated sample produced a flame about 50%  higher than the untreated and the melt pool was correspondingly larger.

It had no other noticeable effect on the burning, just used up wax at a faster rate.

js

[schmidling]

Both these wicks were 6" long.  The one on the left was not treated and the one on the right was treated with the borax/salt solution.  After drying overnight in the air, they were both dipped in wax.

They were lit at the same time and both burned for about one minute.  Clearly something useful resulted from the treatment.

js

[Borek]

Looks like the one treated is much more rigid and the burned part doesn't get down and doesn't touch the wax. In the case of a thick candle it might be less important, but in the case of a thin one, say less than an inch, it might substantially change the way the candle behaves/burns.

Can you try them for much longer, like half an hour? A minute is barely enough to get pas the initial stage of the burning.

[schmidling]

Looks like the one treated is much more rigid

It's actually extremely fragile but that fact it is still there is amazing.  The other just went up with the smoke.

> In the case of a thick candle it might be less important, but in the case of a thin one, say less than an inch, it might substantially change the way the candle behaves/burns.

That's a whole new issue and drip-less candles are more magic than science.

The diameter of the candle must be larger than the melt pool and that depends on the burn rate of the wick and the melting temp of the candle wax and a million other variables.

I have never succeeded in making a drip-less candle that didn't drown in its own melt pool eventually.

>Can you try them for much longer, like half an hour? A minute is barely enough to get pas the initial stage of the burning.

At 6" for one minute that would require a wick 15 ft long and I don't see what it would prove.  In the real world, wicks  burn in candles. 


js

[Borek]

At 6" for one minute that would require a wick 15 ft long and I don't see what it would prove.  In the real world, wicks  burn in candles.

Not sure what you refer to. Does the candle burn at 6" per minute? That sounds super fast, normal candles I used burned at inches per hour, not minute. Thick ones even slower. Or do you mean burning just the wick? If so, that's not I meant - I was asking for leaving the candle lit for longer.

In my experience during first minute the wick have barely enough time to char. Typically later the upper part starts to disappear (whatever the exact mechanism is). So as long as I see the long, charred wick that is most likely just the initial part of the process, not the later, dynamic equilibrium.

[schmidling]

Not sure what you refer to. Does the candle burn at 6" per minute?...
I was asking for leaving the candle lit for longer.

There is no candle in the experiment with the pics.  I was simply comparing the way the wicks burned in air. How it performs in a candle depends on the candle parameters.

All the experiment shows is how the wick burns.

I think it suggests that the treated one will be consumed at a slower rate and produce a larger flame in a given candle.

The way to test wicks is to burn them in blocks of wax large enough to dissipate all the heat so the flame produces a melt pool represented by the nature of the wax and the wick.  The size of the pool gives an indication of the type of candle it will support.

A proper wick should burn until the flame suffocates from CO2.

A poor wick will drown in the melt pool before it gets deep enough to suffocate.

I have been doing this stuff for years without the  Borax and mostly with commercial wicks.  The reason for my post was to get an explanation of the chemistry of the Borax in the wick and why I was not getting the expected results.

js

[Borek]

I was simply comparing the way the wicks burned in air.

OK, I misunderstood the situation.

How it performs in a candle depends on the candle parameters.

IMHO you can't treat them separately - what happens when the candle burns is a combination of both candle parameters (radius of the candle, viscosity, melting point and boiling point of the wax) and wick properties (how rigid it is, how it behaves in different parts of the flame when exposed to different temperatures).

The way to test wicks is to burn them in blocks of wax large enough to dissipate all the heat so the flame produces a melt pool represented by the nature of the wax and the wick.  The size of the pool gives an indication of the type of candle it will support.

That's incomplete for me. The moment the melt pool has reached its final size you got to the beginning of the dynamic equilibrium stage I mentioned earlier. Yes, that will tell you what candle size to use with the given wick. But it still doesn't tell the whole story, as it is too early to tell you how the wick behaves later - will its length above the wax stay constant (preferred way)? Or will it change/grow, changing the speed at which the candle burns? That's when the longer test should come in handy and give additional information.

And as I wrote earlier: I was always under impression is the later stages when the borax treatment start to change the candle behavior.

[schmidling]

Bottom line is:

 A 2" diameter candle with treated wick burned for 4 hours continuously and needed no attention.

Same candle with untreated wick, would only burn for about an hour before nearly going out.  Relighting after cooling produced the same results.

Question:  Borax is good.... why?

js

[Borek]

I have done all this several times and compared the burning characteristics in both candles and the wick alone and find if anything, the untreated works better.

A 2" diameter candle with treated wick burned for 4 hours continuously and needed no attention.

Same candle with untreated wick, would only burn for about an hour before nearly going out.

So, when should I believe you, when you say untreated works better, or when you say treated works better?

[schmidling]

.

So, when should I believe you, when you say untreated works better, or when you say treated works better?
[/quote]

Follow the time line.  It was a work in progress and a learning experience.

I believe the one of those was before I changed the wick material.  The original stuff I was using seemed to have something in it which prevented taking up the borax so there was no difference.

js