To create candles that will be effective in magickal or medicinal work, you must use either essential oils or powdered herbs to scent your candles. Synthetic oils, while cheap, are not at all useful. If all you want is a scented candle, fine, use synthetic. If you want a more magickal candle, however, you'll have to purchase quality supplies.
Powdered herbs are certainly the easiest way to make herbal candles. Just add powdered herbs to the melted wax, pour, and there you go. Sort of. If you aren't careful, a candle that includes powdered herbs can actually light on fire, and I don't mean just the wick. When you're powdering your herbs, they need to be really fine. I mean so fine they could float. Otherwise they can actually catch on fire, acting as a second wick and really ruining your day. And never, ever, put herbs on the top of your candle, even if you think it looks really pretty. You'll light the wick and suddenly everything will be on fire. No good.
The other thing to watch out for is concentration. If the herbs are too concentrated, you'll end up with a fire no matter how fine the herbs are. This means you can't add too much of the powdered herbs to your wax. Add no more than a single tablespoon of herbs to a full pound of wax. Seriously. And make sure the herbs are evenly disturbed throughout the wax. This should help you avoid any unexpected fires.
Essential oils are another problem altogether. You might think you can just add them to the wax, and you can, but heat breaks down the essential so it's really not the easy. There's a reason most commercial candles are made with synthetic oils. But you're not using synthetic oils, are you? Are you?
No? Good. To effectively use essential oils to scent your candles, you need to use a low temperature to melt your wax. If it takes you an hour to melt that pound of wax, that's great. Good temperature. Keep it low and do not add hardeners to your wax. Just don't. It won't work out well.
As for how much to add, well, I find that no more than 2 ounces for a pound of wax is best. 1 ½ ounces is even better. If you're trying to convert an herbal recipe (that uses essential oils) into a candle recipe, see the 'drops' used in most recipes as 'parts' and you should be fine, as long as your total oil doesn't exceed 2 ounces. Also, don't add a base oil when crafting candles. They really don't need it. It only takes away from the small amount of oil you can add to your wax without creating a problem.
Once final warning, add your herbs or oils right before you pour the wax. Heat breaks things down no matter how low the temperature. So add colors and such before you add herbs and oils. Make sure your herbs and oils are distributed evenly, then pour your wax immediately.
Candles may not be the most common herbal preparation, but they are at least easy to make and use. Take advantage of them when you can.
