Simple Dent Removal With Dry Ice
The Cheapskate's Solution
Dent removal is a necessary part of keeping your car looking good. Every time the original shape gets bent out by unfortunate twists of fate, bad weather and minor accidents it creates one more mar on the surface of your ride. If you're clever and cheap, you can fix these problems without special tools and for less than $5 most times. However, it bears mentioning that minor dents in any sort of metal or appliance, ranging from simple dents in your car door to damage on metal roof tiles to popping out dents in a clothes dryer (a risk for those who wash more than just clothes). But the steps below are catered towards automotive maintenance.
Park your car somewhere out of the heat and direct sunlight. Wipe down the dented area and clean it off so that there's no dirt or dust stuck in the dent. It's similar to cleaning a wound before you treat it and stitch it closed. If your car's been kept hot and out in the light, give it time to cool down. You want as little temperature changing as possible.
Once your car has cooled down a bit, take a piece of dry ice and press it against the dent for between 5 and 10 seconds. Make sure that you're wearing thick gloves that protect you from the cold and the chemical makeup of dry ice. Move the dry ice in slow circles to evenly saturate the area with the cold. Pull the dry ice away from the car's panel and watch as the dent reforms into a flatter panel again. If the dent doesn't pop itself out completely after a minute or so, re-apply the dry ice for another 5 to 10 seconds, and continue the pattern until the dent is popped out, or won't come out any further.
What happens is that the dry ice is causing a temperature change in the metal. When the metal gets cold, it essentially shrinks microscopically, creating tension across the metal. This tension makes the metal squeeze the dent in the panel, pushing it back up into its original dimensions. It's a lot like how, if you had a blanket with a weight in it and you pulled that blanket taught, it would create tension and pop the weight up. If done fast enough it would actually pop the weight up hard, creating a trampoline effect.