Gelcoat blisters, also called osmotic blisters, The Pox, and chicken pox, are those unsightly bumps on the surface of a fiberglass/gelcoat hull. Blisters are caused when water permeates the gelcoat layer and accumulates in voids beneath it. More water is pulled into the voids, causing them to expand and create blisters. If left unchecked, water can eventually permeate the fiberglass laminate. When this happens, this water mixes with the acidic, water-soluble materials in the laminate, and continues attacking and decreasing the strength of the laminate.
Blisters can be caused by leaving your boat in the water for long periods of time, but they have also appeared on newer hulls as a result of improper manufacturing. Blisters can also happen if a barrier coat was not applied properly, or if no barrier coat was applied at all beneath the antifouling paint.
Preventing any paint adhesion problems or blistering begins before applying the antifouling paint. Using a quality epoxy barrier coat primer before painting your boat hull creates a an ideal surface for the antifouling paint to adhere to, and waterproofs the hull to prevent blisters. Using a good epoxy is only the first step. To make sure you have an excellent waterproof barrier you must make sure the hull is clean and free of any antifouling paint. It is wise to use a generous amount of epoxy over the entire boat for maximum protection. Sanding and reapplying an addition coat will ensure that you hull will be safe from blistering.
Even though blistering may only be a cosmetic problem is it wise to fix the problem especially if you are selling your watercraft. It is a fact that blistering and cracks can depreciate the resale value. Stop blistering and cracks before they happen. For more tips on keeping your powerboat or sailboat properly call (800) 497-0010 to speak with our tech support team.