Osmosis Survey

Osmosis Testing with a Moisture Meter

Used to determine if excess moisture is present in areas of the hull that may not be visible to the eye. Moisture can be present without delamination occurring and this can pinpoint potential problem areas.

This type of testing may be undertaken on a vessel that shows signs of moisture intrusion around fittings, blisters, or soft spots in the transom stringers and bulkheads. However, this test is not an infallible way to test for moist areas. Many variables come into play when using a moisture meter. These include delamination, bottom paint, voids in the lay-up of mat and resin, water in the bilge, and the length of time the boat has been out of the water. Elevated moisture meter readings are not conclusive evidence of moisture intrusion or laminate deterioration. Readings must be interpreted in context, and confirmation of certain conditions may require invasive examination or laboratory testing.

Osmosis Treatment Monitoring

The values in the photo below do not represent percent moisture content but are relative values. A systematic moisture survey of the accessible underwater hull is performed, with readings recorded and documented. Areas of interest are examined in greater detail, and the results are presented with supporting photographs and measurement records.  During an osmosis treatment, moisture measurements can be repeated at documented locations to monitor changes as the laminate dries. Once the hull has reached an appropriate condition for repair, laminate restoration, fairing, barrier coating, and antifouling can proceed according to the selected repair system.

More information about Blisters and Osmosis

Additional reading: this PDF contains the two-part series by Steve C. D’Antonio published in Ocean Navigator: “Fiberglass blisters and barrier coats” and “Blister analysis and repair.”

Read Blisters and Osmosis (PDF)