How to Fix Car Dents With Bondo Plastic Metal

by Chris Nickson

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Bondo Plastic Metal is a product commonly used for filling dents and cracks in metal surfaces, usually on automobiles. It’s built up gradually in thin layers until the dent or hole is filled and level with the surface of the metal, but it should only be used with dents no more than 4 inches in diameter. Each layer is lightly sanded before the next one is applied.

Filling a Dent

Step 1

Sand the dent and the surrounding area (about 2 inches all around outside the dent) with the orbital sander using 180-grit sandpaper all the way to bare metal. This will remove the wax and paint. Sand carefully to remove any rust in the area, as rust will deteriorate under the Bondo. Clean with a tack cloth.

Step 2

Squeeze a thin layer of Bondo from the tube into the dent using an applicator knife or a putty knife; the thinner the layer you apply, the quicker it will dry; keep in mind that you only have a few minutes to work with it before the plastic metal begins to dry. Smooth out the layer with the knife as much as possible as you apply it. Allow to dry, then sand lightly with 220-grit sandpaper until smooth. Clean with a tack cloth.

Step 3

Apply a second layer of Bondo and leave to dry, then repeat the sanding and cleaning. Build up the Bondo layer by layer, allowing each layer ample time to dry – the drying time will depend on the weather, with clear sunny days offering the fastest drying time.

Step 4

Apply the final layer of Bondo and sand smooth with the metal surface. Squeeze a little of the Bondo onto your fingertip (wear latex gloves) and rub into any small grooves or scratches in the Bondo surface to smooth it out. Paint after the Bondo has fully hardened.

Fixing a Crack

Step 1

Sand the area all around the crack with the orbital sander and 180-grit sandpaper, being sure to remove all the rust and that the edges of the crack are even (that is, that the metal doesn’t curl up). Clean with a tack cloth to remove the dust.

Step 2

Squeeze a small amount of Bondo on the edge of the crack and smooth with the applicator knife. Apply more to the other edge of the crack and leave both to dry before sanding lightly with 220-grit sandpaper and then cleaning with the tack cloth.

Step 3

Apply more Bondo to each edge, allow to dry, then sand and clean. Repeat the process until you’ve filled the crack with the Bondo. Sand for the final time, and use a little Bondo on the fingertips to fill in any scratches. Leave to dry hard before painting.

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