Defects and Grading after Kiln Drying Hardwood Lumber Sawn from Small-diameter Logs

Jan K. Wiedenbeck, Matthew S. Scholl, Paul R. Blankenhorn, Chuck D. Ray


Close inspection of black cherry (Prunus serotina), sugar maple (Acer saccharrum), and northern red oak (Quercus rubra) lumber, before and after kiln drying, revealed the factors that can affect the quality of kiln-dried lumber from small-diameter logs. Species-specific kiln drying schedules, with modifications formulated by a kiln drying expert, were employed in this study to determine if alternate drying protocols could improve the drying outcomes. Overall, the stability/instability of the lumber grades of individual boards after drying compared with before drying was significantly diminished based on the species and applied drying schedule. Most lumber defects were typically attributed to stresses that occurred during the drying process and were more prevalent in the post-drying inspection, with bow defects being the exception. The modified kiln schedules improved the drying defect outcomes for the black cherry and red oak compared with the conventional schedules for these species. For the sugar maple, the schedule-based improvement was less consistent. For the black cherry and red oak, the percentage of boards whose grade decreased during kiln drying was approximately 10% lower than that of the lumber that was dried using the modified kiln protocols. Sugar maple had a smaller change of 7%.


Small-diameter hardwoods; Lumber recovery; Lumber grade; Dry kiln schedule; Drying defects

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Welcome to BioResources! This online, peer-reviewed journal is devoted to the science and engineering of biomaterials and chemicals from lignocellulosic sources for new end uses and new capabilities. The editors of BioResources would be very happy to assist you during the process of submitting or reviewing articles. Please note that logging in is required in order to submit or review articles. Martin A. Hubbe, (919) 513-3022,; Lucian A. Lucia, (919) 515-7707, URLs:; ISSN: 1930-2126