Bondo

Bondo is a two-part polyester-based body filler widely used in automotive repair to fill dents, gouges, and other surface imperfections on metal panels. The system consists of a resin component and a reactive hardener, which are mixed to produce a putty that cures to a hard, sandable surface. Fillers may also incorporate mineral fillers to adjust texture and workability.

Application typically begins with cleaning and roughening the damage area, followed by mixing the resin and hardener in the recommended ratio and adding any filler to achieve the desired consistency. The putty is applied with a plastic spreader, shaped to match the surrounding contour, and allowed to cure. After curing, it is sanded smooth and primed before painting.

The material bonds best to clean, dry metal and is used for shallow repairs on body panels, fenders, and other surfaces, as well as for wood and fiberglass in some cases. It is not designed for structural fixes, and over-thick deposits or repeated flexing can lead to cracking, shrinking, or moisture entrapment if not properly sealed.

Safety considerations include vented work areas and protective gear, as the filler contains volatile solvents and may release fumes during curing and when sanding. Use gloves and respiratory protection as needed, and follow local disposal regulations for waste.