Types of candles - Container candlesMuch unlike other types of candles, like pillar candles or votive candles that are poured into a lould then unmolded when hard, container candles are meant to be burnt in the very container they've been poured into: they're like a candle and its holder in the same package.
That's why the selected containers must not only meet safety standards and be able to stand the heat of the flame without bursting but must also meet aesthetical expectations.
Though they look quite simple, container candles actually are tricky to make, especially when you can't use a specially formulated container wax blend...
Shapes and materials
Not all containers can be used to make container candles, far from it!
First requirement: the material must be able to stand the heat produced by the candle flame. Remember that the melt pool of a paraffin wax candle averages 180°F (82.2°C). To be on the safe side, you don't want to use any container that won't stand a temperature of 212°F (100°C). Quite easy to check: dip the candidate container in boiling water during a few minutes. If it bursts, well... you'll know you shoudn't have used it to pour a container candle :-)
A second important point is the material itself. If plastic has no problem with hot or even boiling water, it won't really appreciate the proximity of a flame. Rejected.
To create container candles, use preferably glass (thickness is an issue, don't use too thin a glass; apothecary jars are great and much appreciated), metal (decorated tea boxes, candy boxes or, why not, tin cans,...), terra cotta (but some of them need a little preparation, I'll explain that), large shells, ceramics,... that's about it.
Don't even think of using wood, cardboard or any flammable material! If you really, really want to use a flammable material, use it as a shell for a glass container, for example.
There's a third element that needs consideration, even if it's not that evident at first sight: the shape and the size of the container.
The general shape of the container should be straight or widened (the top must be larger than the bottom) and free of important differences in its diameter (you don't want to use a sand glass-shaped container). Don't forget that a correct candle diameter/ wick size ratio is a main key to the correct combustion of a candle. If the diameter of the candle varies, you'll have a hard time finding a suitable wick size.
Moreover, the height of the container shouldn't be more than 12 centimeters (5 inches). Higher a container and the oxygen flow will gradually be made difficult as the candle burn, with lots of soot as a result and, possibly, the candle flame going off.
For the same reason, the width of the container must be sufficient and should never be less than the half of its height (eg: a 10 centimeters high container must be at least 5 centimeters wide).