The burn test

A wick chart gets you close, but only a burn test tells you whether a specific mould, a specific wax, and a specific wick actually work together. Trim the wick to about six millimetres, light the candle, and let it burn undisturbed for one hour for every inch, two and a half centimetres, of the candle's diameter: a three-inch pillar gets a three-hour first burn, a one-inch taper gets one.

At the end of that time, look at the melt pool the flame has made. It should have reached all the way to the wall of the mould or container, not stopped short partway across, and it should be between six and thirteen millimetres deep.

Anything markedly shallower or deeper than that range tells you the wick is wrong before you have burned through a whole candle finding out the hard way.