Trees are things of lasting beauty, likewise wood is lasting providing it is used correctly. The best way to use wood is the way it is in nature. And the best products to use on wood for lasting protection are derived from nature.
Wood is a natural material that is in effect dead soon after it is created. The tree is alive only in a thin layer, the cambium layer of living material just under the bark. When the wood is no longer sapwood it becomes heartwood which is dead. Wood is composed of cellulose, protein and carbon. When wood is alive it is converting to proteins; after it dies the proteins start to break down. As these proteins wash away all that is left is cellulose wall and carbon.
Wood is the structural support and in some cases food storage area for the tree. The leaves are periodically alive, gaining water and nutrients from the soil and returning mineral rich food to the roots for storage. The food is made with chlorophyll in the leaves as a result of the energy of the sun. Wood the center supporting structure for the rest of the tree including the roots, is made on the surface under the bark with each years growing season. Each year the previous growth ring dies and becomes the wood that we use today. Each ring represents a years growth. The ring is actually two rings; one thicker (wider & softer ring) made up of the greater growth pattern of the spring when water is plentiful and the other forming a thinner (narrower and harder ring) made during the hotter dryer part of the summer.
All wood fibers are made up of microscopic (or larger) aligned pores through which the water and minerals flow up and the food flows down. The flow down is accomplished by gravity but the flow up requires several physical principles. The water is drawn up the xylem (the name for the upward pores) through respiration (evaporation) of the water in the leaves creating a vacuum that pulls it up. Hydrostatic pressure on the roots as well as the capillary actions of the thin pores (pipes or tubes) also raise minerals. The xylem also has very small one way valves that keep the water and minerals from flowing backwards (down). As the food flows down it travels down through the phloem, the name for the downward tubes.
An easy way to remember which is which is by saying each word out load and listening how they sound. Xy-lem sounds upbeat and ends on an up note. Phloem ends on a down note and also sounds like the word “flow” which indicates flowing down. Remember xylem-up and Phloem-down.
This explanation is lengthy but necessary in understanding how wood weathers or endures. An old saw is 'to put the wood the same way as it grows in nature'. In other words put the outside of the wood out. Application of this principle is evident in the traditional technique of setting fence posts. Poles were placed in the ground upside down; this was to prevent the wood from sucking up ground water by its natural capillary tendency to do so.
When finishing wood the importance of the grain needs to be considered. For exterior applications this is very important. Hand split shingles last for years (¼ inch per century rate of deterioration) because the grain is not open, it doesn’t soak up water as readily. If the wooden shingles are sawn then the grain or pores are opened up and water can soak into the wood, hastening deterioration.
When using wood, lumber and timbers, the way that the material occurs in nature must be respected. It grows that way for a reason. Centuries of evolution have made trees capable of living for hundreds if not thousands of years. They last because of how they grow. In order to insure that wood endures it needs to be positioned relative to how it grows in nature. This point can’t be over emphasized. It’s just easier to work WITH nature than AGAINST.
When wood is finished or treated with oils and other products, all of the above information must be considered. The natural wood should be treated or finished with natural products such as linseed oil, beeswax and turpentine, synthetic petroleum distillate plastics are not at all like wood.
Wood is a homeostatic material, in other words it will adjust to the surrounding environment. When the wood is exposed to dry and warm surroundings it shrinks across the grain. Very little shrinkage occurs along the grain (from top to bottom). When wood is exposed to cool or warm temperatures and high humidity the fibers swell up and the wood expands. Wood is usually cut green and seasoned. As the contained captured moisture (bound water) dries from the wood fibers, shrinks. Oils can also be used to control how and at what rate the wood dries out. In order to assure that the wood doesn't crack and warp as it seasons the ends of the logs or timbers are sealed in order for the wood to cure evenly. If wood is worked while green it should be sealed with an oil (linseed and turpentine mixture works well) to maintain a constant rate of curing and minimize seasoning or shrinkage damage.
With a rigid plastic coating on or in its surface, wood is no longer able to adjust to seasonal changes. causes warping, cracking and damage to the wood while purportedly offering "protection". Polyurethane have a negative rating for protection against water, while waxes like beeswax are the highest rated materials for moisture protection.
Finishes like linseed oil, beeswax, turpentine, shellac and other natural resins and gums have long bond molecules and elastic properties that allow them to move with the changes in temperature and humidity, while protecting and enhancing the woods surface. These are natural materials (gums, oils and resins) that work well with natural materials (wood). The long bond molecules (are long but thin) penetrate in and moisturize the cellulose cell walls to replace the missing moisture with soluble fats. The huge sticky polymers such as gums, resins and waxes form deposits the surface and finish and protect the wood on its exposed surfaces, again working with, not against nature.
Natural finishes have been around for centuries; the Egyptians used natural gums and oils to finish their wooden objects. Traditional finishes have stood the test of time and continue to satisfy both craftsman and customer. These mixtures were used continuously for centuries by master craftsmen and work or they wouldn’t have been used. They were the very best treatments for use on wood. Some people today have lost sight of the how wood behaves or are not sufficiently informed as to the nature of wood to understand how it must be finished. Wood must be finished in a manner similar to how the wood will behave with seasonal changes. The finish must adjust to the movement of the wood, it must be such that it can constantly change and still protect the wood. The finish and the wood must act together. Hard plastic films can’t move and the wood will invariably be damaged.
Thought goes into constructing a piece of furniture so its parts will work together, such as loose panels in frames to allow for movement. The same thought needs to go into how a piece of wood will behave when its finished. Making allowances for movement in the framework is counteracted when the finish doesn’t allow for movement. Use what has always worked. And use it in the way it occurs in nature.
