Osmotic blistering is a condition in which water penetrates the gelcoat of a fiberglass boat, causing swelling and bubbles.
Osmotic blistering explained
Osmotic blistering in fiberglass boats refers to a chemical reaction that can occur when water penetrates the outer layer of the hull, causing chemical reactions that can lead to the formation of small bubbles or blisters under the gelcoat. When you pop a blister, it will smell like acetone.
The water molecules that penetrate the fiberglass can react with impurities that are left over from the manufacturing process. These reactions can produce chemical compounds that create a high osmotic pressure that causes the blisters.
How to prevent osmotic blistering
To prevent osmotic blistering in fiberglass boats, a barrier coating is typically applied in the form of a primer under the bottom paint to prevent water from penetrating the fiberglass.
Treating osmotic blistering
Steps
- Clean the area: Before you begin repairing, make sure to remove all dirt, oil, and grease from the affected area on the boat. Use a degreaser and a clean cloth to clean the area.
- Remove the damage: Remove the affected area with a chisel or a sander and any soft fiberglass.
- Wash the area: Wash the area and degrease it thoroughly with acetone.
- Dry the area: Allow the treated area to dry thoroughly for at least 24 hours.
- Repair the area: Apply an epoxy putty to the affected area and smooth it out with a spatula. Allow it to harden according to the product instructions.
- Sand the area: Sand the hardened epoxy putty so that it is level with the surrounding areas.
- Prime the area: Apply a new primer to the repaired area. Apply the primer in several evenly distributed coats with a brush or roller. Remember that the primer must be compatible with your bottom paint.
- Polish the area: Polish the repaired area to give it a smooth finish.