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Dear Sir
or Madam,
Does your Weatherseal product allow the log to "breath"?
Duane,
Coatings don’t have lungs so they can’t breathe. (Just a joke.)
All coatings allow water vapor to migrate through them. The density or tightness
of the coating determines the rate at which the water vapor can pass through
it. However, no multiple coat, film forming wood stain can handle a high
volume of moisture passing through it without problems occurring; problems
such as mildew growing beneath the coating and peeling. That is why it is
so important to make sure that the logs are dry (18%) if you are going to
apply more than one coat of most stains. For instance, if you read the literature
of Sikkens that claims breath ability (micro porosity)of their coating,
they also state in their directions that the wood needs to be around 18%
MC. In my mind if a coating is breathable it should be able to handle much
high moisture contents. It is semantics.
The penetration issue for wood stains is a misunderstood and an erroneously
held concept by a lot of log homeowners. Penetrating stains, ones that don't
form a film, are usually low solids coatings that, because of the minimal
amount of resin solids in these products, deposits small amounts of resin
on the surface. Essentially these types of stains color the wood but provide
no significant protection. They don't peel because there is not enough protective
material on the surface to peel. Protection and longevity comes from the
type and amount of resins, pigments, fungicides and water-repellents employed
in the formula. There must be some film on the surface of the wood for the
stain to adequately separate the wood fibers from the elements. The other
family of stains that don't peel are non-drying oil stains, usually paraffin
mineral oil stains. These types of oils don't form a continuous film. You
can put motor oil on a piece of wood and it won't peel either. But there
is reason non-drying oils are not generally used as the basic component
in wood stains. For one thing these types of stains make good dust magnets.
They take a long time to really dry and is why the surface often needs to
be wiped free of excess oil. More importantly, oils do not hold up well
to the elements because their chemical structure limit their ability to
provide good UV and weather resistance. Often they do incorporate pigments
into these stains but there is a tendency for the pigments to leach out
of the oil.
The bond of WeatherSeal to the wood fibers is important. How well the coating
adheres and wears depends on the surface preparation of the wood to be coated
and the internal moisture content of the wood. Also, the amount and type
of pigments used in the stain and the degree of weather exposure will play
a significant role in how rapidly the coating breaks down. If you choose
a lighter, more transparent color, its ability to partially block the effects
of sunlight is less than a more pigmented system. Consequently a lighter
stain allows more UV to penetrate the coated wood fibers. The wood fibers
the stain is adhering (as well as the stain) will eventually erode and effect
the mechanical bond of the stain to the wood fiber. The outcome is a release
of the stain coating from the wood fibers.
Moisture and location plays a significant role in this erosion process.
The action of wind, sand and dirt can also be an important factor in the
rate of surface degradation. A log home situated in a treeless field is
especially vulnerable to abrasive weathering. Solid particles in combination
with wind can have a significant sandblasting effect.
Additionally, if the surface is not cleaned properly or the stain is applied
in cold temps, etc, the life of the stain is shortened because the surface
profile or the conditions of application did not allow WeatherSeal to secure
a good bond. If applied correctly to a wood surface that is properly cleaned,
WeatherSeal normally does not peel to any great degree. As it reaches its
service life, WeatherSeal will start to break down and erode off the wood
surface. At that point, you pressure-clean the logs and apply a new coat(s)
of WeatherSeal.
Michael McArthur
The Continental Products Co.