If you enjoy burning wide jar or pillar candles, odds are good that the candle will come with three wicks in it instead of just one. That's because the wider the candle, the larger the wick required for it to burn properly -- and after a certain point it becomes more practical to place three smaller wicks in the candle than one massive wick in the center. You also get the side bonus of three flickering flames instead of just one, and a stronger shot of fragrance than you might get from a single wick.
Basic Safety Principles
The basic principles of safe candle use are the same, no matter how many wicks your candle has. Place your three-wick candle out of reach of children and pets in a draft-free area -- and never leave it burning unattended. Trim all three wicks to about a 1/4 inch before each use, including the first time out of the box; most candle manufacturers leave the initial trimming to you. Remove any and all mushrooming -- carbon build-up -- on any of the wicks before each use.
Three-Wick Burn Pattern
If a three-wick candle has been wicked properly, each wick creates its own melt pool. As the pools expand, they merge into one pool, roughly triangle-shaped, then finally expand out to the edge of the container or candle. If the burn pool never reaches the edge of the candle, the wicks are probably too small. One exception to this is candle bowls, which might at first seem to have wicks that are too small -- but if wicked properly, as the wicks burn lower, any lingering wax on the outer edges of the bowl slides down to join the wax pool at the bottom of the bowl.
The three-wick candle's first burn is the most important; let it burn until the wax pools evenly across the top of the candle. This may take several hours, depending on the size of the candle and the wicks. Let the candle burn until there's an even melt pool across the top of the candle -- every time you light it. If you decide to burn just one wick at a time, still do the first burn with all three wicks -- then alternate between wicks for the single burns, so that you keep the level of wax more or less even across the surface of the candle.
Troubleshooting Your Candle
If your three-wick candle isn't burning evenly, verify the candle sits on a stable, level surface. Check the wicks next. If you trimmed one wick shorter than the others, its melt pool will be smaller. Drafts are another possible culprit; try rotating the candle about 180 degrees and waiting to see if that evens out the melt pool. If the wicks burn evenly, but all the melt pools are too small and won't extend out to the edge of the container, try wrapping a sheet of foil around the edges of the container, leaving the top open. This helps to expand the melt pool, but pay attention, as the wax at the outer edges begins to cool as soon as you remove the foil.