How to detect and treat a hull affected by osmosis

It is not always easy to detect osmosis in a hull. Only when blistering can be seen, it is easy to check if the hull has osmosis. If the blistering, blisters (usually of different sizes) contain a brown coloured liquid with a vinegar odour, it is reason to believe that the hull has osmosis and an osmosis treatment must be initiated. If blisters are dry and hard, they are the consequence of air or solvent retention during the painting works, which has no effect on the fibre glass.

If blisters are not visible, this does not mean that hull is osmosis free: as we seen in the ”Osmosis process” explanation, the process requires a certain time before blisters are likely to appear. Furthermore preventive treatments will not stop the osmotic process, so it is advisable to get the hull inspected by a professional who can confirm any osmosis status or potential. If so, a repair treatment should be initiated as soon as possible to avoid the progression of osmosis. 

If a full osmosis treatment has to be carried out, the gelcoat must be removed completely, the hull must be left to dry and the Jotun Yachting Osmoshell system should be applied to the fibre glass before any primer or antifouling. The most important point is to replace the gelcoat with the correct thickness with epoxy products which are much more waterproof than gelcoat.

Treatment of osmosis