Fiberglass resin additives are crucial for effective repairs. Fiberglass resins, either epoxy or polyester, do not have the structural properties to make significant repairs without some help from additives or admixes.
Additives are used to change the consistency of resins to prevent sagging before the repair has cured or provide other beneficial properties to the mix.
Other additives provide more "body" to the resins to allow lightweight, easily sanded, repairs to be formed.
Yet other additives are specifically designed to make the repair more abrasion-resistant.
When considering the proper additive to use in a particular application, it is important to realize that there are trade-offs associated with each choice.
Any of the powdered additives, such as Cab-o-sil, or the West Systems products, reduce the wetting ability of the resin mix. Therefore, we don't recommend the use of cloth or tape with additives. Use additives to make a filler to provide the final shape of the repaired area.
Also, the additives used for fairing are easy to sand, but are EXTREMELY sensitive to abrasion. On the other hand, admixes to provide a hard, abrasion resistant surface are nearly impossible to sand and shape.
On our repair pages, we will recommend the specific properties of additive for each application.Back to Fiberglass Basics from Fiberglass Resin Additives