candle's black smoke deposit seems not to be electrically conductive

(This is the first topic of the "failed experiments" group.)

I was wondering if the black smoke of the candles could be electrically conductive (carbon) when deposited as a layer over a piece of glass.
After a quick and basic experimentation, it seems it is not.

Here is how I proceeded :
- I've put a piece of glass over the flame of a candle so a black smoke deposit appear on its surface.
- I did so that it becomes opaque (if you want to try, be careful that the piece of glass may break because of the heat)
- then, I used two crocodile clamps to make the contact (I've put a certain depth of aluminum foil between the claws of the clamp and the piece of glass)
- then, I tried to measure the resistance with a multimeter, but the multimeter displayed no value at all.

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What about drying a graphite based lubricant on to the glass, it would be conductive and much less effort, also it would form unfirom structures that should be conductive mainly due to the way that graphite is assembled...
Hey, I did not know there was "graphite based lubricant" !

I've started to look on the net (french hardware stores) : the few lubricant containing graphite that I've found so far, all contains molybdenum disulfide (or something) ...

I will investigate this track a little more =o)
Thanks for the idea !
You could try making a paste of graphite powder in water or something that will evaporate- it might be more conductive than carbon black but would probably be an even more fragile coating so would need you to lacquer over the surface or something to hold it in place.
Lemme know how that goes, hmm if it works I have an idea, quarries use graphite lubricant but I might find some around the builders in our street, I still live in a building site.
Goodhart9 years ago
Analysis of hydrocarbon soots shows it containing different carbon nanostructures. Investigations of carbon nanopowders revealed the presence of the amorphous carbon, carbon with small graphitic sheets or fullerene-like structures. The soot morphology depends on the hydrocarbon mixture and experimental parameters. In other words, depending on the composition of the wax of the candles (natural wax {bees}, paraffin, etc.) how it is combusted, and how much soot is gathered. It may have quite a high mixture of unburned hydrocarbons still in the soot, and would be either non-conductive or have a very VERY high resistance factor.
Patrik Goodhart9 years ago
In other words - candle soot is too greasy, it's not just pure carbon...
Patrik Patrik9 years ago
Let's try to go back to the candle soot. Here's some things to try:

- Build up a very heavy layer of soot on the glass, then try to measure the resistance again. Aim for at least 3-4 times as much soot as you tried before.

- If and when that fails, heating the glass with the soot to a high enough temperature may allow the remaining candle grease to evaporate. Place your piece of glass over a bunsen burner and keep it there for a while. Make sure the glass doesn't start to melt though - that's a different instructable altogether...

- If that still doesn't give you a good conductivity - try compacting the soot layer using a second piece of glass that you lay on top of the first. Maybe the soot is just too powdery to give a good conductance.

I'd be surprised if you couldn't get at least some conductivity using a combination of these...
chooseausername (author)  Patrik9 years ago
Thanks for your ideas =o)

Unfortunately, I don't have access to a Bunsen burner (neither a welding torch or equivalent), so I tried with a simple lighter ... But I did not heated it a too long time, because I was afraid the piece of glass was going to break again.

When try to compact the layer with an other piece of glass, some of the soot glue itself on this second piece of glass, thus, destroying the layer ...

Even with more soot, more compact, and "re-cooked", the multimeter still displayed nothing.
Put it in the oven.
What about a wood fire's soot? Or a gas fire (Bunsen burner)?
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