Bluestaining

Bluestaining is a phenomenon observed in certain types of wood, particularly in hardwoods, where the wood turns a blue or blue-green color when exposed to air. This discoloration is not caused by any chemical reaction but rather by the scattering of light due to the wood's cellular structure. The effect is most pronounced in woods with a high density of small, closely packed cells, such as cherry, maple, and walnut.

The bluestaining effect is often seen in the heartwood of these trees, which is the inner part of the trunk that has been exposed to the elements for a long period. The outer layer, known as the sapwood, remains unaffected. The blue color is not a result of any chemical change in the wood but rather a visual illusion caused by the way light interacts with the wood's cellular structure.

Bluestaining is not a sign of decay or damage to the wood. It is a natural and reversible process. When the wood is cut or planed, the blue color disappears, revealing the natural color of the wood underneath. This phenomenon has been known and documented for centuries and is often used as a distinguishing feature of certain types of wood.

Bluestaining is not limited to hardwoods. It can also occur in some softwoods, such as cedar and redwood, but the effect is less pronounced. The bluestaining effect is also influenced by the thickness of the wood. Thicker pieces of wood will exhibit a more intense blue color than thinner pieces.