OSMOSIS BLISTERING

Osmosis blistering is not just a cosmetic problem. Many people today, including some surveyors, will tell you osmosis is cosmetic and not a structural concern.

Blistering is the first sign that hydrolysis of the polyester has affected at least one layer of the laminate. By the time you spot your first blisters, hydrolysed alkali products in your laminate have degraded the bond between the fibreglass and the polyester resin.

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Studies have shown that a lightly blistered laminate can have a 30% loss of strength. A recent osmosis repair on a 35 Beneteau showed little blistering but actually sustained massive structural damage. The perspective owner was told that the bottom had cosmetic gel coat problems by a surveyor who gave the green light to the new owner. This boat is a great example of misguided advice. In this case osmosis had weakened the entire hull bottom which caused serious fractures throughout the laminate and required a complete hull rebuild, (see photo).