Polyester resin is needed to act as a finish/paste when applying fiberglass sheets. There are multiple components that need to be mixed together to make the fiberglass resin, especially if you want it colored or polished. You should only mix about 16 ounces of resin at a time. The resin begins to harden after 15 to 20 minutes, so any more than this amount will likely harden before you can use it.
Things You'll Need
MKEP (methyl ethyl ketone peroxide)
Bowl or similar container
Polyester color paste
Determine how much resin you will need for the total project. Plan to mix the resin in small batches one at a time if you need to apply a lot of resin that will take more than a few minutes.
Pour the resin into a bowl or other container with a wide mouth. You need a container open enough to easily mix the components.
Add the MKEP catalyst to the container with the resin. You usually need one ounce of MKEP for every gallon of resin, which comes to 1/8 ounce of the catalyst if you are using 16 ounces of resin.
Stir the resin and catalyst together with a paint stirrer or similar wooden mixing tool. Stir it gently and make sure the stirrer goes all the way to the bottom of the container to keep the resin from settling at the top. Stir the mixture until it is about as thick as toothpaste.
Mix in color paste if you want the resin to have color. Use a polyester color paste in the shade you want. The bottle will say if it's intended for use with fiberglass resin.
Include wax powder with the color paste if you want the resin to have a polished appearance when applied.
Mix the resin in an open, ventilated area with no heat sources nearby. Wear long clothing with gloves, goggles and a respirator mask. Tie back any long, free hair.