X-Ray Used in Drying Studies to Detect Honeycomb

Honeycomb is an internal separation of wood fibers, usually along wood rays, that occurs in lumber and other wood products during the course of drying. If dry-bulb temperatures are too severe while free water is still present in the wood, a honeycomb which is strictly internal in origin may develop. Another type of honeycomb (sometimes called a bottlenecked check) may originate from a surface check during the initial drying stages, later extend deeper into the wood, and become tightly enclosed at the surface as stresses are re versed in the latter stages of drying. Since such defects are internal, they usually cannot be detected by surface examination. Soft or low-energy x-ray is an excellent laboratory technique for making nondestructive observations on the development of internal drying defects in thick, refractory lumber or dimension stock. This technique was used successfully to judge the severity of certain experimental pre-dryer and dry kiln schedules for red oak furniture rounds 2 and 3 inches in diameter. A nondestructive examination technique such as this is a distinct advantage in drying studies, where single specimens are used to obtain several kinds of data throughout the test, or whenever the sequential development of surface and internal drying defects is being studied. Periodic x-ray inspection of specimens during the drying process provides a quick, permanent, and continuous record of defect development without destruction of the specimens during any of the inspections. Because radiographic film images are only two-dimensional impressions (unless stereoscopic) of density variations within a subject, radiographs of wood with its numerous possibilities for density variation require careful interpretation. Therefore, any serious radiographic work must be founded on skilled interpretation acquired through comparisons of film images with the actual location, delineation, and identification of included objects within the x-rayed wood specimen.

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