Impregnation of wooden boat is important to guarantee the decay resistance and longevity. We have made an absorption test of impregnating agents to see how VENDIA marine plank reacts with different impregnating agents. The test was made in accordance with Cobb-test, in which the impregnating agents were absorbed 168 hours (seven days) into the test materials. The test materials were normal structured 9 mm VENDIA (called evo1 in the pictures), 9 mm VENDIA Pro (called evo2 in the pictures) and birch plywood. The tested agents were Owatrol, Hempel, linseed oil mixed with zinc naphthenate and tar.
To increase the moisture and decay resistance the impregnating agent should be absorbed deep into the marine plank. For effective absorption it is essential how easily the impregnating agents can penetrate the glue layers of the marine planks or plywood.
The test results showed that all the tested impregnating agents were absorbed into VENDIA marine planks (red and blue bars in the picture) better than into birch plywood. The MUF adhesive used in VENDIA marine plank let the impregnating agents through whereas the phenol formaldehyde used in birch plywood didn’t have the same feature. In practise this meant that the impregnating agents couldn’t be absorbed deep into the plywood.
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The absorption test results of tar were interesting – tar wasn’t absorbed into the wood as well as generally has been thought. The absorption of the tar used in the test into VENDIA or birch plywood was low. The tar only formed a layer on the marine plank’s surface which became thicker when the treatment was repeated. If tar is used it should be greatly diluted to enable proper absorption into the wood.
When impregnating a wooden boat, time and diligence are the key factors, no matter what impregnating agent is used. To increase moisture and decay resistance it is essential to have multiple treatments and a lot of time. The best result can be achieved by spreading the impregnating agent carefully and giving enough time for absorption between the treatments.