Bondo

From CosplayWiki

Bondo is a two part polyester putty filler initially developed by the Bondo corporation to fix dents in automobiles. Once the putty sets, it becomes extremely hard. The Bondo’d surface may be sanded, primed and painted.

Using Bondo poses significant health risks. The fumes are very toxic and the individual compounds are corrosive. Prolonged exposure to the skin will result in burns. Use a mask and gloves in addition to using Bondo in a well ventilated area.

When working with Bondo it feels like the consistency of a liquidily silly putty. When you mix Bondo make sure you are doing it in a cup and applicator you can throw away. Using a plastic cup and a Popsicle stick is a good way to start.

When you apply Bondo you will save yourself a lot of time of sanding in the future if you can make it as smooth as possible when putting it on. Though you CAN hand sand bondo with sand paper it will take much time - therefore it is suggested to use an electric handsander.