Brown stain makes the appearance of ponderosa pine shop lumber look dark, streaky, and splotchy, which often results in lumber downgrading.
For 6/4 ponderosa pine shop lumber, an antistain schedule can typically result in drying times in excess of 100 hours.
The objective of the current investigation was to further develop a kiln schedule with an initial high-temperature component that could reduce drying time while not increasing brown stain effects that influence grade, value, color, and lightness to the point of the pine shop lumber being downgraded due to the brown stain.
Three kiln schedules were used to dry 6/4 (38-mm) ponderosa pine shop lumber with two replicates per schedule for a total of six runs.
Due to the secondary manufacture nature of pine shop lumber, we felt it was important to further explore the color and lightness of the shop-grade boards after they were finished planed and graded by a certified pine shop grader.
This research supports our hypothesis that high temperatures (above the boiling point) can be used early in shop-grade ponderosa pine drying schedules without substantially impacting lightness, color, value, or grade of the shop lumber to the degree a certified mill grader would downgrade the pine shop wood.
The purpose of this study was to develop an initial high-temperature kiln schedule to more rapidly dry ponderosa pine shop lumber without increasing the occurrence of kiln brown stain.
Ponderosa pine shop lumber is often sawn from the relatively-clear sapwood of large-diameter logs and is used to produce furniture, doors, windows, and other high-valued secondary wood products.
Unfortunately, these mild schedules often result in drying times of more than 100 hours for 6/4 ponderosa pine shop lumber.
The objectives of the current investigation were to determine whether the timing (early, late, or continuous) of high kiln temperatures affected the formation of kiln brown stain in ponderosa pine shop lumber and the grade, value, and color and lightness changes in that lumber.
Four kiln schedules were used to dry 6/4 (38 mm) ponderosa pine shop lumber with two replicates per schedule for a total of eight runs.