Osmosis products

Osmosis is recognized as the main enemy of fibre glass hull boats. Osmosis occurs as a result of water vapour and humidity transmission through the gelcoat layer, affecting the fibre glass lamination and its structural resistance.

About osmosis

The osmosis process

Osmosis is the natural process of liquids to equal the differences in pressure between the humidity content of the hull and the sea water. The gelcoat is not a totally waterproof barrier, so humidity will penetrate through the gelcoat down to the fibre glass laminate. 
Other factors that contribute to the development of osmosis, are water and moisture in the bilges. This moisture will also penetrate the laminate from inside, thus enabling osmosis to occur. The speed of the osmosis process and the damage it may cause is depending on several factors, such as production speed, glass fibre quality, water temperature etc. Osmosis is a potential problem for gelcoat hulls in the same way corrosion threaten steel and aluminium hulls. To prevent osmosis, it is important to apply a correct paint system as soon as possible.

How does osmosis occur?

How does osmosis occur?

Osmosis is the process where water is transported through a film, e.g gelcoat, from an area with high concentration of water to an area with low concentration of water in order to achieve equal water concentration in the two areas. These areas may be in the polyester binder itself (yellow area), in the glass fibre laminate (grey area) or between the glass fibre laminate and the gelcoat (red area). After some time, both sides of the gelcoat have an equal concentration of water, which will create blisters with an hydraulic pressure behind the gelcoat.