Over 25 years experience in boat repairs and osmosis treatment
Osmosis is the process by which moisture molecules are transferred through the hull laminate.
It is possible that this laminate will have small voids or air pockets within the resin and between the resin and the glass fibres. Water molecules can collect and condense within these voids.
Within the laminate there will be various soluble components which is a natural byproduct of the boat building process.
When water gets into the voids it dissolves and reacts with these components, this is a process called Hydrolysis. The Hydrolysis will continue within the voids enlarging the cavities and forming a solution which eventually causes visible blisters.
WHAT IS OSMOSIS?
WHAT IS OSMOSIS?
Unfortunately the process will not be reversed by taking the boat out of the water. Voids are increased in size as the pressure within increases.
At some point the pressure becomes too high for the surrounding material to support and a blister is formed.
As this process continues, moisture continues to be absorbed which causes the laminate to break down.
In time some larger blisters may develop within the laminate as well as those more commonly occurring between the gel coat and laminate.
Eventually at this stage, treatment will be required as the structural integrity of the hull can be compromised.
HOW IT EFFECTS THE HULL
HGFR have been treating osmosis conditions in boats for almost as long as it has been recognised (early 70's).
Curing Osmosis involves peeling the hull to remove the blisters (as seen opposite), this reveals the laminate which then requires a series of high pressure steam cleans that ensures any remaining salt deposits and soluble components are removed.
The hull then needs to moisture metered to ascertain the moisture content, then dried by using infrared lamps for an average period of 2-6 weeks (monitoring the drop in moisture content daily).
Once the hull is at a satisfactory moisture content, it is essential to then apply a layer epoxy laminate to provide an additional barrier (epoxy has a much greater resilience to water absorption ver polyester systems).
A two-part epoxy filler is then applied and faired to provide a smooth and accurate finish to the hull before applying the 5 coats of epoxy paint to establish a strong and waterproof barrier against any future water ingress.
The hull is then ready for the antifoul system of your choice. Coppercoat will provide even further protection.