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Osmosis Treatment

What is Osmosis?

Osmosis is a process of degeneration within a glass fibre laminate and it is recognised by the formation of water filled blisters through the laminate.  At first these appear as small pin head blisters on a small area of the hull but as the problem spreads, the size of the blisters increases and eventually the entire surface of the hull will be affected. 

Osmosis is caused by a chemical reaction between water and substances remaining in the manufactured hull, and once inside reacts with the chemical components creating acidic substances.  More sea water is absorbed to balance the concentration of liquid trapped inside the laminate (technically this is called osmotic pressure).  This causes the formation of the well known blisters.

Preventing Osmosis

Prevention is always better than cure and it is possible to prevent osmosis using specialised products that have to be very carefully applied.  It is not always possible to see osmosis developing and the symptoms (the blisters) only appear when the problem is already advanced. 

Preventative osmosis treatment, that effectively creates a second protective skin around the gel coat, can be carried out on new boats or boats that have been thoroughly checked for the absense of osmosis before starting.    Older hulls should be checked with a humidity guage/moisture meter to ensure that water is not trapped inside the protective barrier.  This would create pressure behind the gel coat and cause blisters and eventually cracking.  Once the gel coat is breached in this manner, the underlying laminate is capable of absorbing water like a sponge.  The hull moisture level should also be checked if you think the gel coat has been over sanded when work has been carried out on the boat.   

Once the hull has been checked and is completely free of moisture then the complicated process of applying epoxy coatings can begin to prevent or treat osmosis.

Osmosis treatment

If the stages of osmosis are in an  advanced, and you can see blister formation on the hull surface, either isolated or across the entire hull. Gel peeling(Removal of gelcoat) is needed to expose the bare laminate, and sometimes the first layer of glass is also weak and needs to be removed. This is done professionaly with a gelplane. Layers of gel and glass are planed off the surface of your boat. Once all gelcoat has been removed the next step is to grit blast the entire hull to open up pores and remove weak resin and laminate on the surface.

Once this is done a professional and proven anti osmosis treatment can begin. Every job is different and some hulls require more drastic measures to dry and treat any Osmosis damage.



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