Mottle Candle Technique which was recently posted by Erica of The Bonnie Bath Company on her blog Bath Alchemy - A Soap Blog and More.
What are mottled candles? According to Erica, mottled candles have a snowflake style dimension on the surface. The candle will usually be smooth with a pretty design and can occur in both container and molded candles. The mottled effect is simple to create and is sometimes achieved accidentally. It occurs when oil is added to paraffin wax. Since some fragrance oils are heavier (more oily by nature) than others, they can sometimes create this effect against your will. But when you want this interesting design, adding some oil will do the trick.
There is one caveat about this project is that you will be using paraffin wax and adding mineral oil. So for those who are strictly making eco-friendly candles with soy or beeswax this may not be the project for you.