Directions for How to Use Bondo on a Car

Rust and dents are easily smoothed by plastic body filler.

Regardless of where you live, your vehicle can rust. Parking lot dents and dings are a fact of life for all vehicles. When it comes time to repair a rust hole or a dent, the restorer will undoubtedly find themselves reaching for a can of plastic body filler. This product, which often gets tagged with the brand name "Bondo", has been a staple for body shops and backyard body men for decades.

Things You'll Need

• Rusty or dented car
• Permanent marker
• Sanding block or power sander
• Sandpaper
• Plastic body filler
• Cream hardener
• Plastic applicators
• Paper plates or cardboard
• Window screen
• Grater file
• Primer
• Paint

Instructions

1. Identify the problem. Finding a rust hole is easy; however, finding a small dent or ding takes a bit more work. Run your hand over your body panel and note where you feel a ding. Place a mark on the body panel with your marker where you feel the ding.

2. Prepare the body panel. Using a sanding block with 60- to 80-grit sandpaper, remove the paint from the area requiring body filler. Make random passes at 45-degree angles to each other to ensure a good tooth for the body filler to adhere to. Make sure to work the area out a few inches from the actual rust or dent. This will allow you to be able to feather the filler out.

3. Mix the body filler. Place a glob of body filler (about the size of your fist) onto a paper plate or a piece of cardboard. Apply a line of cream hardener across the body filler (follow your body fillers directions for the proper amount to use), and mix it in until your filler is a consistent color. The filler will begin to harden immediately, so you must hurry with this process.

4. Apply the filler to the panel. Use a plastic applicator and spread the body filler onto the prepared area, making sure to apply all of the filler in the same direction. This will help to eliminate air bubbles in the hardened filler. Apply the body filler in several thin coats rather than one very thick coat. This involves mixing several batches of filler and hardener and allowing the coats to harden between applications. On large rust holes, you can place a piece of window screen inside of the rust hole to help hold the body filler in place and build up a base of body filler off of the screen.

5. Remove excess filler. Once the filler has set up, use a grater file similar to a cheese grater to remove the excess body filler from the repair. Apply light pressure and work the filler in one direction, making sure not to dig a hole with the file. This will save hours of sanding. Perform this step before the filler is completely cured. Once it is completely cured, it is nearly impossible to grate it away. Once the filler is cured, use an 80-grit sandpaper to contour the body filler and blend the repair into the surrounding metal. Use 120-grit sandpaper to finish sand and feather the filler into the body panel. Run your hand over the repair occasionally while sanding to assure you are sanding the surface level.

6. Paint the repair. After sanding the repair to your satisfaction, apply a light coat of primer and allow it to dry. Follow your primer manufacturer's directions for application and apply several light coats until the repair is well covered. Sand the primered repair with a 120-grit sand paper and apply paint to the area following the manufacturer's recommendations for spraying.

Tips & Warnings

• Work with small batches of body filler. The hardener works so fast that you will waste large amounts if you make too big of a batch at once.

• Never work in a dark environment. It will make the ding and dent detection much harder.

References

• Car Craft: Paint Your Car at Home