Why Does Fiberglass Mat Appear White in Fiberglass Products?

This phenomenon is quite common, especially when new resin is used, leading to what seems like poor adhesion and the appearance of white spots. Typically, in fiberglass products with gel coat finishes or added pigments, this issue may be hidden from view. However, the existence of the problem does not disappear just because it is not visible.

In simple terms, it can be challenging for two unrelated materials to bond effectively. To enhance bonding, fiberglass manufacturers often apply coupling agents to the surface of the glass fiber. The efficacy of different surface treatments can vary significantly in terms of their compatibility with the fiberglass. Replacing the resin is a common approach to remedying such issues. While changing the fiberglass is also an option, most people assume that the fiberglass itself is not the problem.