A ton of chips may be wet or bone dry and may be a short ton, long ton, or metric tonne. Chips are also expressed as units and bone-dry units. Even if the same unit of measurement is used, it may not represent the same quantity. A good example is the difference between a board foot in log scaling and a board foot in tallying lumber at a sawmill. Correct conversion factors for some products, such as logs and lumber, vary with piece size.
Wood is variable.
Wood moisture content can vary from a few percent to more than half the weight of a piece. Since wood shrinks and swells as moisture content changes, these changes affect volume as well as weight. Many wood product measurements and conversion factors that are reported are ambiguous because no indication of such conditions is given. While this book primarily focuses on forest products in the Pacific Northwest, several national and foreign systems are included because of the rapid globalization of markets. Because many readers may be relatively new to the industry and its terminology, a glossary is provided and descriptive background on the philosophy and assumptions that underlie formulas and measurement systems is presented.