I did a little science experiment in my kitchen last weekend. I can't say I necessarily recommend these methods, since I'm fairly certain that one wrong move would have sent hot wax and boiling water all over me... But luckily that didn't happen and you can try this at your own risk.
I've been wanting a set of candles in canning jars. Obviously candles should be in canning jars. Everything else works well in canning jars. But I didn't really want to buy a bunch of beeswax and melt it down myself. I can get really awesome 100% beeswax candles at my co-op with my employee discount, so there 's really no reason to make candles myself (this is me talking myself out of making things from scratch that I can easily buy).
The standard candle sizes that I can find won't fit in a wide mouth pint size jar (my favorite size).
Peel off the labels and such from the candle. Fill a heavy bottomed pan with enough water so that it comes about halfway up the sides of an empty pint sized jar. Put that jar in the pan of water (keeping the water outside of the jar only) and place the not-quite-small-enough candle into the jar as far as it will go. The candle should be heavy enough to keep the jar from floating.
Heat the whole contraption up over medium high heat. As the water begins to simmer, press firmly on the candle- making sure to press straight down. [This is where you might scald yourself] Repeat frequently until candle sinks enough to meet the level of melted wax in the bottom of the jar. Wipe any stray wax from the jar rim. Turn off the stove and use your canning tongs to pick up the very hot jar and place it on a dry kitchen towel until it is cool and dry.
So cute! Everything's better in a canning jar.