Yes. You can use old candles to make new ones. The process is pretty simple: just melt the candle down and add it to your new candle's wax. This will give your new candle some of the scent and color of the old one, which is great for those who like to keep their candles around for sentimental reasons.   The only thing to keep in mind is that your new candle won't be as strong or smooth-burning as an entirely new one would be—because of this, we'd suggest mixing only small amounts of old wax with fresh unless you have a specific reason for wanting a more rustic look or scent.