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Author: Subject: Making fumigation candles - sulfur + paraffin = SO2 for pest control and preservative
RogueRose
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[*] posted on 12-1-2017 at 15:30
Making fumigation candles - sulfur + paraffin = SO2 for pest control and preservative


I recently came across a few farmers and green house workers talking about how they can no longer find sulfur candles. Further research into these peaked my interest when I found out the various uses for them besides just killing bugs/insects as they can also be used to preserve various crops from fruits (apples, pears, etc) grains as well as helping to preserve silage (hay/straw bales and such). Now as with all things on the internet, I'm never sure if these are legitimate claims but I would suspect the pest/bug killing would be a definate use but as far as a preservative, IDK at what concentration is needed for this type of use and for how long the fumes need to be present and whether there needs to be a decontamination process after its use (I suspect washing the fruits is a definite before consumption though).

So with this in mind, I thought I would try making a small candle (about 10g). The recipes I found varied from using paraffin flakes and mixing the sulfur into it (mortar & pestle), filling a tin with S powder and inserting a waxed wick to simply pouring a pile of powdered S onto a plate and lighting it. Another recipe called for melting the wax and mixing the S as well.

I thought melting the two together would be most effective so I stated with that. I took about 20g of paraffin (138f melting point) and heated it (in a steel soup can) to melting then added 10g of S and continued heating & stirring until it looked as though it dissolved - but actually it just settled to the bottom in liquid form. I then poured the melted sulfur into a small mould and placed a wick in it. There was about 16-17g of wax remaining that didn't mix with the sulfur, but the melted wax retained some dissolved sulfur as well (guessing about 5-10% by weight). The hardened sulfur has a very hard consistency, much harder than candle wax and close to crystal sulfur hardness. It burns very nicely with a very distinctive SO2 smell.

I also tried adding a wick to powdered sulfur and lighting. while it did burn for a short time, once the wick was burnt to the top of the sulfur pile, the flame went out and the sulfur did not continue to burn - so the wick does not "wick" up the sulfur. This might be due to the container type/shape and air flow so I will try a different approach.

Lighting a pile of sulfur (on flat bottom of soup can) I used a blow tourch to melt then light and it burnt for a few minutes and then went out with a black residue on the top, but with a lot of sulfur remaining.

what I found odd was that some of the old sulfur candles were supposedly just a steel can (totally open top) with a piece of cardboard stuck in it as a wick (non-waxed) and this was supposed to be sufficient to continue combustion of all the sulfur.

As note, I'm using agricultural "flours of sulfur" which is a super fine dust/powder. I know people say that it isn't always that pure but I dissolved some in hot toluene, filtered at 1um, evaped and only lost about .1% total weight. If it was CaCO3 as the additive (as many say it is) then I would have suspected it have filtered out - unless it dissolves in toluene..?

I'm going to try some of these again and take some pics and video. I think the melting with wax is a good method that will yield a working product though may be unnecessary with higher quality sulfur.
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[*] posted on 12-1-2017 at 16:16


I find it puzzling that your sulfur self extinguishes. As a teen with my first Chemistry set (Gilbert) I enjoyed watching sulfur burn with a blue flame. All I did was light it with a match and the burning was self-sustaining. Maybe your sulfur is insufficiently pure or the wrong particle size.



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[*] posted on 12-1-2017 at 16:55


Sulfur from garden supplies is often laced with bentonite -- up to 10% I think. I don't know why. That affects its combustion characteristics. Recrystallisation from xylene gives a much purer product.



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[*] posted on 12-1-2017 at 17:14


Quote: Originally posted by j_sum1  
Sulfur from garden supplies is often laced with bentonite -- up to 10% I think. I don't know why. That affects its combustion characteristics. Recrystallisation from xylene gives a much purer product.


I Googled sulfur bentonite and it said:

One solution is to combine elemental sulphur with bentonite, a type of clay that increases its volume by factor of 3 to 5 when it comes into contact with water.
When a sulphur bentonite granule comes into contact with soil moisture, it breaks apart into fragments of dust-size particles, thus allowing swift and continuous solubilisation.

These small particles have sufficient surface area for the thiobacillus bacteria to convert the elemental sulphur into sulphate form, which is then available for plant nutrition. The smaller the particle size, the quicker the conversion.
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[*] posted on 12-1-2017 at 17:42


Sulfur and paraffin when melted together can produce H2S. I believe at over 150C though.

I once made sulfur candles from pure sulfur as a kid and found a way to make them work. Take many wicks and twist them around each other; for whatever reason single wicks did not work. The wick diameter was around 1/4 inch to 0.5cm after twisting several wicks together. Dip the wick into molten sulfur and let it solidify. Lighting was a bit difficult the first time, and easier following times once the wick was permeated with sulfur. I had to use a torch to get the wick going; it would burn down to the level of the sulfur, then the torch would melt the sulfur around the wick, and finally the wick would become permeated with sulfur and burn with a stinky small blue flame.
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RogueRose
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[*] posted on 12-1-2017 at 17:59


I read the bentonite somewhere as well but also heard calcium carbonate, maybe different uses. Either way, the powder is super fine, the finest powder I have ever seen for a elemental substance, especially for the size/price ($12/50lbs - I have a BIG farming area nearby). It says "pure flours of sulfur". If it had bentonite, I doubt it would have dissolved in the toluene and there would have been some indication in the filter after filtering 1250g (dissolved in hot toluene) - but there was nothing on the top of a 2" diam filter. Usually there is some sludge or something, even if just a little.

Could there be some adulterant that is soluble in toluene that may be causing this? btw, I did't used the filtered/crystalized sulfur for any of this as the filtration results showed no solid particulates, so I just used the powered flour.


As for the wicks, I used a coulpe different types, normal candle wick material (forget size rating, but for a 3" diam candle) as well as using a coffee filter rolled in a way to make a 3/16" wick that was soaked in wax.

I really think it was the container in which this was burning as it may have limited the air flow.

I am concerned about the H2S a little, but I didn't notice the smell from the candle.
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[*] posted on 13-1-2017 at 04:37


If you get it via the agricultural route, there are two forms of flowers of sulphur ( in the UK at least ) - green and yellow, the green is the version with added clay and usually another wetting agent, the yellow is just straight powdered element - it's made by sublimation so should be pretty clean.
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