Have you ever used a candle lamp and noticed that the wax levitates in the jar? There's a reason for that!
You are witnessing a physics phenomenon called Charles's Law in action! When the temperature of gas increases, so does its volume. Heating a gas gives its particles more energy, so they move faster. If the speedy particles have room to spread out, the volume of the gas will increase.
This could happen for a couple of reasons
1- The lamp heating element is too close to the candle
2- It's been on for too long. I would do 3 hours max for safety
In both of these instances, the glass container heated up and the gas is trying to escape. Note: This is a huge safety issue in which the gases can get too hot and expand too much, causing the glass container to explode.
What should you do if you see the wax floating in the jar:
1- Turn off the lamp
2- Allow it to cool completely
Once the candle returns to room temperature, the wax should sink back to the bottom of the container. If it doesn't, use a toothpick to poke a hole in the wax (away from the wick, toward the edge of the glass). Poking all the way through will allow the gasses to release on their own. If you see the candle doing this again, I would use it as a cue to turn off the lamp since we've got combustible gas plus hot, liquid wax at play.
You may also find that the candle doesn't smell like much after being heated. If that happens, the fragrance will have burned off from the top layer. You can pour out some of the melted wax and the remaining should still be quite fragrant.
