Spalted maple is wood characterized by distinct patterns of discoloration and intricate dark lines. These captivating designs are not inherent to the wood itself but result from fungal colonization within it. Fungi interact with wood components, transforming its appearance into a highly valued aesthetic.
The Fungal Architects
Various types of fungi are the primary agents creating spalted maple’s unique patterns. These fungi typically colonize dead or stressed wood, initiating decomposition. White rot fungi, for instance, are significant contributors to spalting, often causing lighter streaks and bleaching effects by consuming lignin, a component of wood cell walls.
Sapstain fungi, another group, produce blue or black discoloration within the wood. These fungi primarily grow in the sapwood, creating visible color changes if enough fungal threads (hyphae) are concentrated. While most mold fungi are not considered spalting fungi, the species that do cause spalting initiate the early stages of wood breakdown.
How Fungi Create the Art
Fungi produce distinctive spalted patterns through several mechanisms. Pigmentation is one mechanism, where fungi generate colors like reds, yellows, greens, or blacks through extracellular pigments released into wood cells. These pigments create vibrant stains, such as the blue seen in bluestain, a result of darkly pigmented fungal hyphae.
Zone lines, the intricate dark lines often seen in spalted wood, form when different fungal colonies establish barriers to protect their resources or territories. These lines are typically composed of hard, dark mycelium (fungal structures) and serve as demarcation zones where competing fungi meet. While zone lines themselves do not significantly affect the wood’s structural integrity, the fungi responsible for their creation often contribute to early stages of decay. This early wood breakdown, known as incipient decay, alters the wood’s texture and appearance without extensively compromising its structural soundness.
Conditions for Spalting
Fungal growth and spalting pattern development require specific environmental conditions. Wood moisture content is a critical factor; wood needs to be sufficiently wet (typically above 20% moisture content) for fungal colonization. However, waterlogged or submerged wood can inhibit fungal growth due to a lack of sufficient oxygen.
Temperature also plays a significant role, with most fungi preferring warm conditions, generally between 10 to 40°C, and rapid growth often occurring between 20 and 32°C. An appropriate level of oxygen is necessary, though fungi do not require large amounts. The process also requires sufficient time for fungi to colonize the wood and develop characteristic patterns, which can range from several weeks to months or even years, depending on the fungal species and environmental consistency.
Impact on Wood Properties
Spalting results in physical changes to the wood beyond its aesthetic transformation. The process can reduce the wood’s strength and density, particularly if fungal decay progresses too far. White rot fungi, for instance, can cause “punky” areas in the wood, indicating a loss of strength and weight. This softening or increased porosity in certain areas can affect the wood’s workability, making it more challenging for tasks like carving or machining.
While spalted wood is highly valued for decorative purposes, its structural integrity is compromised, making it generally unsuitable for load-bearing applications. When working with spalted wood, safety considerations are important. Dust generated can contain fungal spores, which might cause allergic reactions or respiratory irritation in some individuals. Therefore, wearing appropriate respiratory protection, such as an N95 mask, is advisable when handling spalted wood dust.