Blistering and Osmosis on GRP Craft

The problem of blistering due to osmosis on GRP or Glass Reinforced Plastic bottomed craft goes back some years now. The appearance of this problem is large blisters on the bottom of the boat that is caused by water absorption.

It is a common problem among GRP craft and over the history of the problem many products have been said to be the cure. However, research into the problem is still being done. New products are still lining the shelves and finding the product that is indeed the cure is largely considered to still be under way.

GRP moulding is made up of thin glass filaments or strands. This is basically fibreglass. It is a strong and light weight material that is used in many different applications around the world. The glass strands are bound together by a plastic resin. On their own the glass strands are strong but not stiff. The resin is added to add the stiffness.

The osmosis process is basically where water gets in though the spaces between the fibres and the resin. Finding the perfect way to deal with the problem is an ongoing process. In the 70s a change in resin was the answer and as we are still discussing the problem now it clearly wasn't the answer.

GRP Boat Surveys in Surrey

The best way of stopping the issue all together is by having the right temperatures and humidity through the initial build process. Now this of course is completely out of your control unless you are building your own boat.

It is always worth getting a survey of any GRP craft before buying it. As ultimately it is the quality of the resin and the fibre mix that will let you know if the boat will develop osmosis. A bad quality mix can result in osmosis in just a few short months. A better one can mean it takes 18 months or more, the best quality may never get it at all.

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