In this photo you can see the finish has blistered, cracked, and is starting to peel. This has happened because the finish has lost its adhesion. (Notice the top area where the log has become sunburned and turned gray).
One of the factors for peeling is the moisture content of the logs when they were coated. If the logs were too wet (20% or higher), the logs will continue to dry out and as they dry the resident moisture will move from the center of the log outwards to the surface. The moisture will form on the surface of the log between the finish and the wood. If the finish is very thick and heavy, a blister will form because the moisture can't pass through the barrier of the finish. If your logs are still quite green, we suggest that you apply only one coat of a log keeper finish, such as TM5 First Treat or Colorfast. This will give the logs some protection while still allowing the moisture to escape out through the one coat of finish. Once the logs have dried out to 19% or less, then you can apply your final finish. You can test the moisture content of your logs with a Moisture Meter. Also, moisture can also occur from checks holding water. When heat from the sun reaches and heats the log’s surface, the moisture is pulled to the surface causing a break in the wood-to-finish adhesion.
Any type of finish, either oil or water based can peel. Remember, it is the amount of finish build up that will provide the potential for peeling. Penetrating finishes tend to peel less because instead of acting like a plastic coating on the logs, they don't build up into one thick coating (less "plastic") thus, allowing moisture to escape out through the thinner coating. They do tend to weather away over time and will need to be re-coated periodically to maintain their protective qualities.
The gray, sunburned area on the top of the log shown in the picture is a result of prolonged, direct sunlight. This can be prevented in new construction by extending the eaves and overhangs to allow for more protection from the sun. Also, avoid using clear finishes alone because they provide less UV protection from the sun. You could also plant shade trees to help deflect the direct sunlight.
If your logs are sunburned you can typically get by with sanding down the sunburned areas with 60-80 grit and then reapplying your finish. You will need to reapply the same number of coats as the rest of the wall to match the color of the rest of the wall. Tip: When you are reapplying the finish to match the rest of the wall it is better to apply too much and make the sanded areas look darker then to not add enough so they look lighter. The darker areas will tend to look natural where lighter areas will stick out and look distinctively unnatural.
Questions on maintaining the legacy of your wood structure? Give us a call- 1-800-359-6614
Pickup in store - or ship to your door -in whichever woods your cabin dwells.
Schroeder Log Home Supply, Inc.
1101 SE 7th Avenue
Grand Rapids MN 55744
1-800-359-6614
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