In some magical traditions, once a candle is burned it picks up vibrations from things around it -- in other words, a used candle is already tainted by vibrations, and so will lead to a negative or ineffective magical outcome.
Same theory, only now instead of just Most practitioners of magical systems will tell you that, much like a few other aspects of life, size really isn't important.In fact, really big candles may be counterproductive -- a candle that takes too long to burn down can be highly distracting to someone working a spell that instructs you to wait until the candle burns out on its own.Typically, a short taper candle or a votive candle work the best.In some cases, a spell might call for a specific type of candle, such as a seven-day candle or a figure candle, which may represent a particular person.Candle magic is one of the simplest forms of spell casting.Considered sympathetic magic, it's a method which doesn’t require a lot of fancy ritual or expensive ceremonial artifacts.
In other words, anyone with a candle can cast a spell.
After all, remember when you were a child and you made a wish before you blew out the candles on your birthday cake?
One of the most popular candles, believe it or not, is in fact the little menorah candles which are sold by the box in the kosher section of the grocery store.
They're about 4" long, white, unscented, and thin -- perfect for spell work.
You should always use a brand new candle for spell work -- in other words, virgin materials.
Don't use the candles that you burned at the dinner table or in the bathroom yesterday for spell work.