Bondo (putty)

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Bondo is a two-part putty used to fix dents in cars, created by Bondo Corporation. While the term "Bondo" is a brand name for this company's product, it is commonly used in the U.S. as a genericized trademark to refer to all auto-repair putties or so-called plastic body fillers. Bondo is a two-part polyester that when mixed turns into a putty which then sets and becomes rock-hard. The user can apply the mixed Bondo to the dented panel, sand it to the proper shape, and prime and paint it like the metal around it.

Bondo was developed as a replacement for body solder, or sometimes pure melted lead, that was formerly used for the same task. Body solder is more durable, but may require more effort to apply. Solder poses toxic hazards for people and the environment due to heavy metal components such as lead. Despite the fact that Bondo is far safer to work with than its lead based counterparts, it still poses significant health risks. The fumes are quite toxic, and unmixed Bondo compounds can create burns in cases of prolonged skin contact. The use of gloves, a mask, and proper ventilation are all recommended.

When buying a used car, it is possible to check for areas that have been repaired with significant amounts of Bondo by walking around the car with a magnet, as the magnet will not be attracted to the Bondo.

[edit] Formulation

Bondo is based on unsaturated polyester resin, minerals and glass microspheres. The normal formulation of a lightweight bondo body filler is the following: