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I buy lots of candles, which means I end up with lots of candle holders. I want to be able to reuse these containers, in some cases for food storage since some of the candles are in jars. This means I need to completely eliminate all of the wax.

How can I ensure that the container is free of any wax residue?

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  • A minor frame challenge - how about replacing some of the bought candles with home-made, reusing the containers? – Chris H Nov 6 '20 at 10:37
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    @ChrisH I do reuse the leftover wax bits and make "garbage" candles, but I am not looking into turning it into a full hobby :) – jackwise Nov 6 '20 at 15:11
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I've done similar things after using food containers for candles. You may not actually need all these steps, but this is how to be very thorough.

What I'd do is put them in a cool oven, just hot enough to thoroughly melt the wax (100°C should be enough).

First, put them face down supported on wires over a drip tray. The vast majority of the wax will run out.

Then, still hot, and holding using oven gloves, wipe the insides thoroughly with a dry rag.

In terms of food safety, while I doubt you could ever reuse the containers commercially within the rules, I'd probably be happy at that point to use containers from unscented candles. After all, paraffin wax and beeswax are both used in food.

I'd still go a step further though, and definitely if anything scented had been in there: Finally, put them through a dishwasher on a hot wash (70°C or above). Paraffin wax and beeswax both melt a little below this, and once melted the dishwasher will remove the residue and any scent. Shifting the scent may actually be the tricky bit.

Apparently container candles are best made with lower melting point waxes anyway, so they should easily melt in the dishwasher. The earlier steps were more to protect your filters. If any scent lingers after dishwashing, either give up on that container, or wipe round with cooking oil, then fill to the brim with hot soapy water. Dishwash again after soaking.

Of course, there's no guarantee that the containers can withstand a dishwasher. Paint (or glitter etc.) on the outside would be particularly likely to be damaged.

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  • What about if I don't have a dishwasher? Would pouring in some boiling water from a tea kettle do the trick? – jackwise Nov 5 '20 at 21:10
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    I wouldn't pour boiling water in directly. It might break the glass. I'd wash in very hot soapy water - hot enough that you'd want to let it soak for a bit before putting your hands in. That shoudl be adequate though it might not quite reach the melting point. – Chris H Nov 5 '20 at 21:13
  • @jackwise Pouring boiling water in directly might also not break the glass. If you have trouble cleaning it otherwise, give it a try in the sink. Worst case you'll need to clean the shards from the sink. I regularly make tea in glass jars not rated for boiling water, the only time one broke was when I knocked against it when it was already stressed from the temperature. – Nobody Nov 6 '20 at 10:11
  • @Nobody prewarming in merely hot water, or putting in hot water then microwaving (if no metal parts) would be another option – Chris H Nov 6 '20 at 10:33
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    I just tried this with some leftover containers - popped them in the oven for a bit, then gave them a rinse with hot soapy water and an old scrubber. I don't have a wire tray, I just placed them upside down over foil. Worked like a charm! – jackwise Nov 6 '20 at 15:14
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I've recycled several glass candle containers into "whisky glasses". I put a squirt of washing up liquid in the bottom, then poured boiling water in, and left to soak/melt.

After they were mostly clean, rinsed out, then stuck in the sink, again with lots of washing liquid, and filled with boiling water.

Didn't get any breakages, and the "glasses" came out nice and clean - a couple needed a bit of extra scrubbing to loosen any "baked on" wax, but afterwards perfectly usable.

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According to quite a few web sites, but specifically Science Direct, beeswax is insoluble in water, but soluble in a few different liquids.

Beeswax is insoluble in water and soluble in organic solvents, such as ether, acetone, xylol, benzene, chloroform, and tetrachloromethane. In order to completely dissolve the beeswax, the temperature must be increased beyond its melting point (Stefan, 2009).

For paraffin based wax solvents, the Chemistry SE suggests other solvents, specifically toluene or xylene. I have a quart of toluene in my garage, which implies that it was purchased a local big-box store.

Ethanol and acetone are not non-polar organic solvents. Each one has a slight dipole moment; due to the difference of electronegativity between H and O in ethanol and between C and O in acetone. Wax is composed of heavy, long-chain alkanes. And as "Like dissolves like" try to dissolve your wax in toluene or in xylene.

In many of the links I viewed, elevated temperatures are indicated. Not explosive level heat, just warmer than room temperature, perhaps hot hot water temps.

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    Have you had that toluene for a while? It's not as easy to buy in significant quantities as it used to be. I don't think I'd use many of those solvents in something that's going to hold food anyway - even warmed for long periods to drive off the solvent itself, they're often not very pure. – Chris H Nov 6 '20 at 10:35
  • Toluene has serious health risks and is now difficult to get in the consumer market. Xylene is generally available. However, waxes don't easily dissolve at room temperature. You generally need to melt the wax, then slowly mix in the solvent. The solvents evaporate quickly at room temperature, and much faster at the temperature of melted wax. So the process should be done in a sealed environment, not in an open pan. Even if it's a big enough space and small enough quantities to not reach an explosive concentration of vapor, (cont'd) – fixer1234 Nov 9 '20 at 19:29
  • there is a serious fire risk because the vapor is easily ignited from any source of flame or spark even a good distance away, and serious health risks from breathing the amount of vapor generated. Sorry, but -1 because this is bad and dangerous advice. – fixer1234 Nov 9 '20 at 19:29

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