Accidents happen to everyone. People stub their toes or hit their elbows. Similarly, cars get dented and dinged. Whether from a hailstorm, a runaway shopping cart in a parking lot or a tool rolling off a shelf in the garage, sooner or later, a car will show its age. But even a small dent can cost big bucks to repair at a body shop. So it's no surprise that most do-it-yourselfers look for cheaper, easier methods. One such method to fix dents is a simple trick that only requires a few household items and some inexpensive dry ice. The idea is to use rapid temperature change to cause the metal to expand and contract and pop out the dent.
1) Inspect the dent. Using a towel, rub the dent clean and identify the perimeter of the dent. Remove any loose bits of rust or paint from the dent. Note that this technique works best on dents on the car's hood, doors, fenders or trunk that are shallow and cover a wide surface area. Dents with creases or paint damage or dents near the edge of the car tend not to respond well to this technique. Similarly, dents in older cars might not pop out as easily due to the thicker metal panels used.
2) Gather your materials. This technique will require a hair dryer with variable settings, aluminum foil, heavy-duty rubberized or leather gloves or a very thick towel, and dry ice. Dry ice can usually be bought at groceries, and it is fairly inexpensive. Remember that dry ice gives off carbon dioxide, so transport it in a sealed, insulated container such as a cooler. Otherwise, make sure your car is well ventilated during transport and repair. Additionally, five to 10 pounds of dry ice will last only about 24 hours, so buy the dry ice as late as possible.
3) Warm the surface of the metal. Either park your car so the dent receives direct sunlight for a few hours (a perfect time to shop for dry ice) or use a hair dryer to warm the surface of the dent. If using a hair dryer, place it on the medium setting and hold the dryer five to seven inches away from the surface, moving it constantly over the dent to prevent any paint damage due to overheating. Cover the dent with a sheet of foil to further insulate the paint against heat damage. After a few minutes, the panel should be warm to the touch.
4) Apply the dry ice. Remember, dry ice is incredibly cold (-109.3 degrees F, -78.5 degrees C), and direct contact can very quickly cause burns. Use gloves, a towel or even potholders to handle the dry ice and prevent damage to your skin. Apply the dry ice to the foil for a few seconds, making sure to pass the ice over the entire surface of the dent. Remove the dry ice and wait a minute. You may hear the metal in the dent pop back out.
5) Inspect and repeat if necessary. After waiting, inspect the dent. While still wearing gloves, or using a towel, rub your hand over the surface of the foil to assess the dent. If the dent has not completely disappeared, apply the dry ice again. If the dent still remains, store the dry ice and then repeat steps three and four. If at this point the dent still remains, it is unlikely that the dent can be repaired using this technique.
A final word of caution: Although videos of this technique abound online, be aware that this is an amateur DIY technique, and not a technique used by professionals in most body shops. Therefore, although it may save you hundreds of dollars, the dry ice technique might not be on par with the results professionals could achieve with their equipment. Realize that the original accident that dented your car weakened the metal. Rapidly raising and lowering the temperature of the metal may further weaken it. Although the dent might pop out using this technique, there is the possibility that temperature changes might affect the treated area of the car in the future.