Grain and growth patterns part 1
Trees are storytellers if you know what to look for. The life cycle of a tree is told through the grain. Did the tree have a long life? The grain will tell you. Was there a significant drought at some point in the trees life. Again the grain will tell you. Was there a fire? Did the tree suffer an infestation? Did the soil content change? All in the grain.
We all know that you can slice a tree and count rings to tell you how old a tree was but there is so much more to learn.
Just below the bark of trees there are thin layers of cells known as the cambium covering the tree from the ground up. These cells are in a constant state of growth. Half of the cells make either wood or bark while the other half remain in the cambium to grow and divide yet again. Cells on the inside of the cambium will transform to become the interior wood. The cells outside become bark and split again into two layers. The inner bark carries the sugar-rich sap down from the leaves to feed the cambium and roots. The outer bark protects the fragile cambium from invasion by insects, fungi, animals and extremes of heat and cold.
Over the course of 5 to 10 years the wood at the center of all trees undergoes a chemical transformation. In most trees, the transition from sapwood to heartwood is clear because of a distinct color difference. The chemicals responsible for the change are known as extractives. Extractives are very difficult to identify and so plant biologists struggle to understand these processes.
Technically, the word grain refers to the orientation of wood-cell fibers.
Growth rings. As the image above shows growth rings indicate the successive layers of cells as they transform within cambium layer. The science of growth rings is known as Dendochronology. Dendochronology is defined as a scientific method of dating tree rings to the exact year they were formed in order to understand atmospheric conditions during different periods in history. Dendrochronology is useful for determining the timing of events and rates of change in the environment. The single greatest factor understood in the science of dendochronlogy is the climate in which the tree grew. Each ring marks a complete cycle of seasons, or one year, in the tree's life.
Sapwood versus heartwood. As mentioned above there are usually distinct differences between the sapwood and the heartwood. Sapwood is the living, outermost portion of a woody stem or branch, while heartwood is the dead, inner wood, which often comprises the majority of a stem's cross-section. You can usually distinguish sapwood from heartwood by its lighter color.
This piece of newly sawn hickory perfectly illustrates the difference between the sapwood and heartwood. The dark colored areas are the heartwood and the light creamy colors are the sapwood. This distinction is not always apparent but hickory gives a stark example.
Appearances of grain in wood are affected not just by the trees growth cycles but also how the wood is sawn. For a more thorough understanding of how this works follow this link.
So what are you seeing when you look at wood grain? Here are a few basic definitions.
Straight grain. These are the species which grow straight and parallel with the tree’s trunk. Straight-grained woods are easy to use in woodworking and furniture making and comprise the bulk of what we sell at KD Woodscompany.
Spiral: These are trees with the grain moving at a slight upward tilt, creating a spiral-like pattern circling the trunk.
Interlocked: This growth pattern takes spiral grain a step further. The interlocking of grain occurs when spiral-grained trees switch directions causing a spiraling back and forth switching from right-hand to left-hand spirals. Depending on the slant of the spiral, and the total amount of direction changes, these woods can be either loosely or tightly interlocking. This can be seen most clearly on quartersawn wood creating a kind of ribbon stripe figuration.
So what will you see in your flooring? Stay tuned to the next blog to find out!
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