When might osmosis occur?

Osmosis is a process of degeneration within a fiberglass laminate. It is caused by a chemical reaction between water and unreacted substances remaining in the substrate, post manufacture. Typically, water enters the hull substrate through the gelcoat and, once inside, reacts with the chemical components to form acidic substances. These substances create pressure behind the gelcoat, which causes blisters and eventually cracking. Once the gelcoat is breached in this manner, the underlying laminate is capable of absorbing water like a sponge. Osmosis is not only caused by water on the outside of the hull – bilge water from the inside can also cause a problem. It is therefore worth making efforts to keep your bilges dry.