How To Use Body Filler

Body fillers are used for repairing certain small auto body damages like dents, pits or scrapes. They are made of thermal-set plastics, meaning that they harden with heat that is created by a reaction between the filler and the vehicle’s metal surface. While using body filler can be tricky, if you learn the basics, it can help you make very solid body repairs.

Step #1: Preparation

If you want to fix a dent using auto body filler, the first thing you must do is clean the area that you want to repair. For this, all you need is a mild automobile soap, a bucket filled with warm water and a soft clean sponge. Use the sponge to wash the damaged area using soap and water to rid it of any excess dirt, rust or grease. Next, use a rugged, 80-grit sandpaper to sand the surface and remove any paint or substantial debris that are on the surface. This will ensure that the body filler has an unfinished surface to adhere to.

Now add some body filler to a flat surface, like a mirror or piece of cardboard, and mix it with a small strip of cream hardener using a putty knife until the color is consistent. Generally, a 1 1/14-inch strip of hardener will mix well with about a golf ball-sized dollop of body filler. Once the filler and hardener are mixed together, they should be applied to the body within three to four minutes.

Step #2: Application

Now that you have your well mixed concoction of body filler and hardener, you are ready to apply it to your damaged area. Apply the first coating using your putty knife over the sanded area, making sure to spread the filler mix firmly and liberally. Also, spread the filler about two to four inches around the area you want to fill in order to ensure a uniform body contour once the filler has been hardened and sanded down. Now, leave the filler to harden for about 30 minutes before sanding. Once the filler has hardened, use an 80-grit sandpaper block and sand horizontally across the filler area back and forth. Using a crisscross motion, sanding evenly five times in one horizontal direction and five times in the opposite direction to work the filler faster.

If need be, apply more layers of filler and repeat the sanding process until the entire affected area is smooth and consistent with the rest of the vehicle’s body. Finally, using a 180-grit sandpaper, blend the edges of the body filler so that they are flush with the unfilled metal edges. Once all the filling and sanding is done, apply primer, paint and polish as needed, and you will have successfully repaired the body of your vehicle.

To learn more about body filler and for more DIY car tutorials, be sure to visit

Leave a Reply

Back to top button