A.Preservation consultant John Leeke responds: You are right; rot does indeed require water. Wood rots, or decays, when fungus organisms eat it. Three conditions must be present for the fungus to thrive: temperatures between about 40°F and 100°F, food (which is the wood itself), and a wood moisture content above 20-25%.
The presence of the fungus is a given because fungus spores are everywhere, carried about by the wind. Two common types of wood-eating fungus are "cubic brown rot" and "white rot." Cubic brown rot eats the cellulose component of wood, leaving the darker brown lignin component, which shrinks into characteristic blocky...
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