Just say the word ‘osmosis’ and you will surely strike up a lively conversation. Here are some of the myths, misconceptions, and untruths about osmosis:

• osmosis does not exist
• this is not osmosis, just a small humidity absorption
• you do not need to cure it; it will go away by itself
• the osmotic process is a natural phenomenon which cannot be entirely avoided
• osmosis occur only on new boats
• osmosis occur only on older boats
• generally osmosis do not appear during the first 4-5 years of boat's life
• that treatment does not work, because osmosis occur right after curing ( usually said about a good treatment wrongly applied)

Needless to say that all of the above are often heard around the yard, but are just not true.

Osmosis is a chemical-physical phenomenon, happening during the migration of a solvent, in this case water, through a film separating two liquids with different salinity concentration.

Air bubbles into the laminate, more or less close to the gelcoat surface, are the basic requirement to produce osmosis. First, water migrates through the laminate to fill the blisters; water will then start to solve every material it can: glass-fibres, undercured resin, etc. At the end of this reaction, the new solution will attract more water through the gelcoat, so that the pressure inside the bubble will grow and expand.

This phenomenon will go on as long as the hull is in the water; the blister that started out at 3 to 4 millimetres in width will increase, due to the inside osmotic pressure, with time and permanence in the water. In other words, once started, the osmotic process will continue without any possibility to appraise beforehand the speed at which it expands.

It can then be said that osmosis is a degenerative disease which does not stop by itself unless the hull is kept out of the water; even then, and after months of being sheltered, the liquid may be present in the laminate and, due to the fiberglass' permeability, it will move along the fibres.

This is why, after a while, bubbles appear smaller due to reabsorption.

Why my boat?

Some primary causes of osmosis:

• poor gel-coat quality, in the case it is made with a poor moisture permeability resistance resin: nowadays, in order to obtain the best guarantee of low permeability no solvent resins are used.
• poor moulding practice so that a void content in the laminate is created
• use of excessive catalyst during the lamination process
• poor workshop environmental conditions (too cold or too humid)
• presence of impurity or solvents in the glass fibres or in the resin

What do the blisters look like?

• The blister should be round shaped: this is due to the internal osmotic pressure which is constant in all directions.
• The blister must deform gelcoat surface.
• The blister must contain liquid.

The removal of the gelcoat is the first stage of any osmosis blistering treatment and peeling is widely accepted as the most effective system for guaranteeing an assured repair. The GelPlane has well documented advantages of quality of finish but further, with the dust extraction system the workplace remains clean which is friendly to the environment.

The GelPlane provides a convenient and controllable method of gelcoat removal. The depth of cut is set by readily adjustable shoulders which position the blades relative to the hull. The GelPlane will peel as easily on concave curves as on convex and is versatile enough to cut over spray rails around skin fittings and between bilge keels.

The Yachtsman is now the only marine repair facility in Eastern Ontario using the GelPlane gelcoat removal tool for treatment of osmosis.

The GelPlane leaves the hull smooth and fair and free of any osmosis blistering. The hull is now ready to dry out and then receive an epoxy barrier coating to seal the hull and prevent further water migration.

GelPlane Demo