What causes osmosis blisters on fibreglass boats? #boating

Fibreglass osmosis is a phenomenon that occurs in fibreglass boats and structures.
It is a type of water-induced damage that affects the laminate layers of fibreglass.
Osmosis occurs when water molecules penetrate the laminate layers of fibreglass.
Osmosis can occur in both polyester and epoxy resin-based fibreglass structures.
The damage caused by osmosis is often referred to as 'blisters' or 'blisters in the gelcoat'.
The blisters are caused by the expansion of water molecules as they move through the laminate layers.
The blisters can appear as small bubbles or large, raised areas on the surface of the fibreglass.
Osmosis can be caused by a variety of factors, including poor quality resin, poor workmanship, and exposure to water for extended periods.
Osmosis is most common in boats that are kept in the water for long periods of time.
Osmosis can also occur in boats that are stored on land if the humidity is high.
The severity of osmosis depends on the extent of the water penetration and the condition of the fibreglass structure.
Osmosis can weaken the fibreglass structure over time and make it more susceptible to other forms of damage.
The blisters caused by osmosis can be repaired by sanding down the affected area and applying a new layer of gelcoat.
The repair process can be time-consuming and expensive, especially if the damage is extensive.
Prevention is the best way to avoid fibreglass osmosis.
Regular maintenance and inspection of the fibreglass structure can help identify early signs of osmosis and prevent further damage.
Keeping the fibreglass structure dry and well-ventilated can also help prevent osmosis.
Properly applying an epoxy barrier coat during the initial construction of a fibreglass structure can also prevent osmosis.
The barrier coat acts as a waterproof layer between the fibreglass laminate and the water.
Epoxy barrier coats are more effective at preventing osmosis than polyester resin barrier coats.
There are different types of epoxy barrier coats available, including high-performance epoxy coatings that offer superior protection against osmosis.
Fibreglass osmosis is a common problem in older boats and structures.
The problem has become less common in recent years due to improvements in fibreglass materials and construction techniques.
Fibreglass osmosis can affect the resale value of a boat or fibreglass structure.
It is important to address any signs of osmosis as soon as possible to prevent further damage and maintain the value of the fibreglass structure.