Things You'll Need
Bucket with lid
Bondo auto body filler
Polyester fiberglass resin
A gel coat is a specialized resin often used for the surface coat on fiberglass products. It is thicker than standard resin, allowing you to build up a solid shell before adding layers of fiberglass. You can make your own gel coat using fiberglass resin and Bondo auto body filler. This gel coat has a pink color, and makes it easy to visually inspect for thin spots. The mixture is also often less expensive than commercial gel coat.
Empty a container of Bondo auto body filler into a 1 gallon bucket with a snap-on lid.
Add an equal amount of fiberglass resin to the Bondo.
Mix the two components together into a creamy paste using a paint stick. Mix slowly to avoid introducing air bubbles.
Seal the lid onto the bucket. Use a marker to write the amount of catalyst required from both the Bondo and resin instructions onto the bucket.
Store the mixture in a cool place.
To use the homemade gel coat, measure out the amount that you need in a paper bucket. Mix in the proper amount of both Bondo catalyst and resin catalyst, following the mixing ratios that you copies from the original containers.