End Coating Effects on High-Temperature-Dried Yellow-Poplar

The effectiveness of end coatings in reducing the amount of end checking in high-temperature-dried yellow-poplar was investigated. End coatings have been shown beneficial at temperatures below 180? F; however, very little information is available on their effectiveness at high temperatures. Four coatings–a silicone rubber sealant, a plastic roof cement, a neoprene/asphalt coating, and a urea-starch coating–were separately applied to the ends of 4/4 lumber. Different boards with each end coating were dried with two separate drying schedules: 1) 300?F dry bulb (DB) and 180?F wet bulb (WB) for 2-1/2 hours or 2) 300?F DB and 180?F WB for 2-1/2 hours followed by a 1-1/2 hour conditioning period at 200?F DB and 190?F WB. Coated and uncoated ends had the same degree of visible end check with the first schedule, and coated ends had more visible checks with the second schedule. The application of an end coating had little effect in reducing the rate of moisture loss from the ends of boards when drying at temperatures of 300?F. When conditioning at 200?F, end coating the boards prevented moisture from being readsorbed on the ends of the boards. Consequently, steeper moisture gradients and more end checking occurred than in uncoated boards. The benefits of end coating high-temperature-dried lumber is questionable; therefore a determination of these benefits should be made for each species and high temperature schedule before deciding to end coat boards during high-temperature drying.

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