1. Freeze the Candle Wax
Cold causes wax to harden and shrink, making it easier to remove. Use a butter knife—or a spoon if your wax is soft—to break up any large chunks of wax that remain in the container if the jar has a narrow mouth. Place the candle in the freezer for several hours or until it is frozen. The wax should pop right out of the container, but you can also loosen it with a butter knife if necessary. Scrape off any residue and then clean the container with soap and water.
2. Use Boiling Water
Hot water can also be used to remove wax. Put the candle on a surface protected with a towel or newspaper. Use a butter knife or spoon to remove as much wax as you can. Pour boiling water into the container, leaving room at the top. (If your candle is made of a soft wax, such as soy wax, you can use hot water that’s not boiling.) The boiling water will melt the wax and it will float to the top. Let the water cool and remove the wax. Strain the water to get rid of any small wax bits. (Don’t pour wax down the drain.) Scrape any remaining wax and clean with soap and water.
3. Use the Oven
This method works well if you have several containers to clean at once. Scrape out as much wax as you can with a butter knife or spoon. Heat the oven to 180 degrees and line a rimmed baking pan with tinfoil or one or two layers of parchment paper. Place the candles upside down on the pan and set the pan in the oven. The wax will melt in about 15 minutes. Remove the pan and place on a heat-safe surface. Hold the container using a towel or pot holder and wipe the inside with a paper towel. Let the container cool and then clean with soap and water.
4. Create a Double Boiler
Remove as much wax as you can with a butter knife or a spoon. Place the candle inside of a pot or large metal bowl on a heat-safe surface. (You can put a folded dish towel under the candle to keep it from moving in the pot.) Pour boiling water into the pot around the candle, making sure that the water does not get into the candle jar. Let the jar sit in the hot water until the wax has softened. Hold the jar in one hand and use a butter knife to loosen the wax. Remove the container from the water, pop out the wax, and then wash with soap and water.
(content from Clever.com)