Blisters are water pockets found within the hull of a boat, due to water absorption into the fiberglass. These water pockets can damage the hull and spread over other parts, which could compromise the structure of the vessel.

Our job is to find these blisters using a moisture reading device.

We will open up the blisters to flush out the acids (glycol), clean with fresh water, and then proceed to treat the affected area with resin-fillers, making sure that the repaired area is even with the rest.

An initial report from URI, issued in 1986, identified the principal cause of blisters as the presence of water-soluble materials in the hull laminate — from chemicals in the resin, or from dust, dirt, and sawdust. As water molecules combine with these materials penetrate the laminate, they form a droplet of solution. Because of osmotic pressure, more water molecules combine with this droplet, eventually expand enough to cause a blister.

The solution formed by water mixing with the water-soluble materials in the laminate is acidic, and more concentrated than pure water. Osmosis a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane. (The semipermeable membrane in this case is the fiberglass laminate). The new mixture attracts more water, expands, and causes the blister. Most of us don't think of our fiberglass hulls as having the characteristics of a sponge, but studies show that fiberglass laminates do indeed absorb water.

The generally accepted industry method of blister repairs has been to use epoxy resins mixed with chopped glass or powder, after first making sure that the epoxy is compatible with the polyester used in the hull laminates. Our certified technicians specialized in this type of repairs. Careful consideration is given to these important issues.