Osmosis Treatment
The water enters the hull through the gelcoat and once inside, reacts with the chemical components creating acidic substances. Any unprotected hull is likely to show signs of osmosis eventually, the exact length of time before osmosis occurs depends on many factors including: the type of water in which the hull is moored, the temperature of the water and most importantly, the quality of the original hull construction.
Once osmosis has developed it may not need repairing straight away it can sometimes be left for many years before remedial action is required. When it is finally treated it is important to get it done by a company well versed in treating this condition.
Our preferred method of treatment is when the hull is dry to apply a layer of laminate prior to the epoxy coatings. We first did this 20 years ago and have to date not heard of one of our re-laminated boats having recurrent osmotic blistering.
Osmosis is not only caused by water on the outside of the hull - bilge water from the inside can also cause the problem. It is therefore worth making efforts to keep your bilges dry.
In some cases, reactive impurities in the gelcoat and laminate will cause osmosis in the earlier life of the boat. This is a structural problem and should be referred back to the boat manufacturer. Approximately 15% of osmosis cases are accounted for in this way and will normally become evident within the first three years of the boat's life.
