wick candles

The wick of my tea candle was buried in wax. So I lit a piece of paper and stuck it in the wax. Now the wax is burning off the paper, as if that were the wick.

The wax itself wouldn't light on fire without a wick, yet clearly what's burning is the wax, since the paper would have long ago burned up. What's going in here?

  • $\begingroup$ I recently watched a video in which it was said that ash acts as a catalyst when trying to burn a sugar cube. Burned paper/pick probably has a similar chemical composition as ash, so could act as a catalyst. I do not know enough about chemistry in order to tell if wax burns in a similar way as sugar and why ash acts as a catalyst in the first place, but maybe this gives you some insights. $\endgroup$ – fibonatic Jun 15 '15 at 2:47
  • $\begingroup$ Also: the really "long wick" of the twisted up paper burned through that candle faster than the small wicks. You can see the flame is bigger in the picture, and it used up the wax faster. $\endgroup$ – isomorphismes Jul 11 '15 at 19:11

In a sense, wax does not burn, at least not in the same way that, for instance, magnesium burns. Instead wax gets hot and vaporizes, and the vaporized wax is what burns. The heat of combustion vaporizes more wax, and the process continues.

A candle wick works by forming a conduit for the pool of melted wax which forms around the base of the exposed wick. The melted wax is transported up the wick by capillary action, vaporized by the flame, and combustion takes place.

When you light a candle, it starts out by actually burning part of the wick, which provides enough heat to melt some of the wax and the candle can then burn normally.

Wicks also need to be sufficiently stiff, or they will curl over under their own weight and either accumulate in the wax pool or spill over down the side of the candle.

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    $\begingroup$ A candle that has never been lit before will often have the wick soaked in wax so that the wick doesn't mostly burn away the first time it's lit. If the wick is impregnated with wax before it is lit (either by the manufacturing process or because it has been lit and the molten wax rose up the wick before solidifying as the candle cooled) then almost none of the wick is consumed before the flame is mostly burning wax vapour. $\endgroup$ – CJ Dennis Jun 15 '15 at 8:21
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    $\begingroup$ Additionally, the reason the pool of wax does not vaporize and combust as a runaway reaction without requiring a wick is that it takes very high temperatures to vaporize. The wick allows a small amount of liquid wax to run up the wick thermally isolating it from the rest of of the pool allowing it to be heated to the required temperature to vaporize. $\endgroup$ – Rick Jun 15 '15 at 13:24
  • $\begingroup$ It is indeed possible to achieve the required temperature for the pool of wax (or paraffin, stearin, etc) to burn without the aid of a wick. Once we had a fondue set for christmas that consisted of a terracotta base holding three tealights and a bowl on top that could be filled with chocolate or cheese. After lighting all the tealights, some time passed and we noticed that the whole device was now giving off much more light than at the start. Examining it we found that the three tealights essentially merged into a single huge flame that was impossible to blow out. $\endgroup$ – zovits Jun 15 '15 at 14:32
  • $\begingroup$ Thanks for this quick answer! I'm going to wait to see if others roll in before accepting. $\endgroup$ – isomorphismes Jun 15 '15 at 15:57
  • $\begingroup$ re: the stiffness comment. I think you can see in both of those photos that the paper lighter is mostly totally out of the wax. (Also the flame with the wide paper is burning more than the narrow wicks.) Which I think puts your comment in context: people want a thin wick that will burn through the candle wax slowly. Yes? $\endgroup$ – isomorphismes Jun 15 '15 at 19:07

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