Sapwood and Heartwood – Know the Differences
To achieve high-quality woodworking, knowledge about wood is a must. Projects can succeed or fail based on which part of a tree is used. In particular, it’s important to know the difference between heartwood and sapwood.
The Parts of a Tree
Knowing how a tree grows sheds light on which part of a tree is best for your woodworking project. A tree trunk is composed of the following basic parts, listed in order beginning with the outer layer:
- The bark is dead tissue; and its function is to protect the tree from weather, insects, disease, fire, and injury.
- The phloem is a thin layer comprised of living cells, and its basic function is to transport food around the tree.
- The cambium is living tissue. This very thin layer of a tree produces both new phloem on one side and new xylem on the other.
- The largest part of a trunk is the xylem, which is composed of both sapwood and heartwood.
What is Sapwood
Sapwood is new wood and is like a pipeline that moves water through the tree up to the leaves. Essentially the working component of a tree, sapwood transports water and sap similar to the way blood flows through our veins, capillaries, and arteries.
You can usually spot the difference between the two distinct parts of the tree’s xylem if you were to view a crosscut of a mature hardwood tree’s trunk. Once you remove the comparatively thin outer layers, the tree is essentially made up of sapwood, which is lighter colored wood, and heartwood, which is darker in color.
Lumber cut from sapwood shrinks considerably as it goes through the drying process. This part of a tree is also far more susceptible to fungus than the center of the trunk.
What is Heartwood
The central, strong pillar of a tree is heartwood. As new rings of sapwood grow, the inner cells are put out of commission and become heartwood. Although this portion of the tree is dead or retired sapwood, it doesn’t decay. As long as the tree’s outer layers are intact, heartwood remains strong.
What occurs as moisture is no longer transported through the straw-like cells, the pores in Heartwood are filled with organic material. The presence of chemicals called extractives causes the cell walls in heartwood to change color. Extractives are what create the rich color and unique character in the heartwood.
The functional beauty of heartwood for a woodworker is threefold. First, it’s significantly less susceptible to fungus. Secondly, heartwood contains far less moisture than sapwood and will have far less shrinkage when it’s dried. Thirdly, heartwood becomes in some ways as strong as steel as the fibers are bound together.
Free Download – 6 Reasons Your Wood Project Failed
Regardless of whether the woodworker is working with sapwood or heartwood, the correct moisture content of the wood is critical to meet the demands for the end use of the product being made. A high-quality, accurate moisture meter is, therefore, a must for the serious woodworker.
Make sure to use the most accurate wood moisture meter to check the moisture content of sapwood or heartwood.
As Sales Manager for Wagner Meters, Ron has more than 35 years of experience with instrumentation and measurement systems in different industries. In previous positions, he has served as Regional Sales Manager, Product and Projects Manager, and Sales Manager for manufacturers involved in measurement instrumentation.
Last updated on July 29th, 2021