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Seasoning

Seasoning is the natural step of stabilizing wood in an environment where it is stored. Often, air drying is not enough to meet the destination environment. However, seasoning is the most important step in preparing wood.

Moisture in wood

When trees are standing, water is distributed from the roots to the tip. To make wood contain less moisture, cutting trees in the season that they stop distributing water is preferred. Some people even say that during a new moon is the best time to harvest trees because of gravity.

Wood contains two kinds of water. One is distributing water, called free water, and the other is the liquid in fibre cells, called bond water. As wood dries, free water is lost first. When bond water starts to be lost, the wood shape starts to transform. This is called the saturation point.

Wood can grow fungus or stain. Also, pitch in wood runs until the moisture content is below 20 to 25 percent, depending on the wood and the species. This is another reason that wood needs to be dry before it is used as material.

Balance of shape

Trees try to stay standing plumb with the help of wood fibre. Some areas are windy and sloped. To make trees stay in position, fibre puts tension against the direction of the wind. It compresses on hillsides and puts tension on the other side on slopes.

This balanced tension is in the memory of wood fibre. This balance is the most stable when trees are standing. When trees are harvested, they become logs. Logs are still stable because all the fibre is connected. When logs are milled into timber, this is when this balance is lost. As timber dries, it moves with the tension memory that the wood contains. This will continue until wood moisture settles in its final destination environment.

Did you know?

In Japan, Horyuji is a 1,400-year-old wooden temple. The timber used on the west side of the temple was brought from the west. The posts stand as the trees grow. The builders knew that was the best way to make timber stable because the memory is in the fibre. They also split timber not milled because the fibre is fully connected if not cut off.

According to the builders' knowledge, wood lasts three times the age of the wood when the tree is cut down. If wood is 100 years old, for example, it lasts for three hundred years. It increases strength for one-third of the time, it contains strength for another third, and then it starts to die. A scientist here in Canada said that this is not true, but I don’t know who I should believe.

In Japan, all structure posts are stored upside down, Gravity is used to season the timber. Each store has its own brand, and the store brand is stamped on each timber. Then, when carpenters use these posts, they use them in the direction that trees grow, so the stamp is upside down.

There are many truths in wooden temple knowledge, and it is hard to ignore what the ancient temple builders have told us.

Straightness of grain

Straight grain results from trees growing in easy environments. It doesn’t mean that the trees are stronger, but that they are much more stable. As wood transforms during the drying process, straight grain wood doesn't twist as much as spiral grain does.

If we apply joinery before wood is dried, you can imagine what happens afterwards.

Drying timber

Drying timber is a difficult process. Air drying is a natural way of drying. It sounds best, but it tends to check the wood more compared to kiln drying. Steam kiln drying is an effective way of drying smaller dimensions, but it can dry only the surface of timber.

Vacuum and radio frequency (RF) kilns have sealed chambers, so they can bring the boiling point down. That is how these drying methods check wood less than air drying does. As far as we notice, these two methods affect only how timber is dried. Vacuum kiln drying applies the heat from the outside, and RF uses electricity, boiling the wood from the centre. Vacuum kiln drying takes 10 to 12 days, while RF takes only one-third of that time. Because of RF is powerful, it can cook the fibre if the drying coordination is applied improperly.

We use the vacuum kiln drying method.

Wood age

Trees have age, just like humans do. Older trees are more stable but not as strong as middle-aged trees. Younger trees move more and are not ready to use. Tight grain is what we prefer, but the grain can be too tight because it will start to lose strength at some point.

As trees grow in one season, they grow faster from spring through summer and more slowly from fall through winter. That is what we see in tree rings. Tighter grain means less space in fast-growing fibre. This space in looser grain is where the moisture stays, which is why tighter grain is more stable than looser grain. Density is also heavier in tighter grain. The increased density means that the wood is stronger.

British Columbia's forest resources are managed. Forestry management controls when trees are planted and harvested. Trees that come out of these managed forests are about 50 years old, and the size of the butt (bottom) is about 14 inches. This means that the trees contain 50 rings in seven inches, or seven rings per inch. The wood we are sourcing has 8 to 13 rings per inch, so it is around 100 years old or older.