March-April 2018

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Page 38 of 43 PalletCentral • March-April 2018 39 airborne. Also, because the bluestain fungi do not digest the wood cell wall, they have minimal impact on the wood structural integrity. In other words, although it looks harmful, it will not decay the wood. Sun Exposure If your wood product is left outside and exposed to the sun, over time it will darken (like a sun tan) and may make the wood appear dirty or damaged. The impact of sun exposure causes a chemical change in the tannins of the wood that, over time, react to the sun's exposure. If this happens to your wood packaging product, or other lumber product, it's said to be "weathered." Enzymatic Discolorations Red alder, oaks, beech, maples, and other hardwood species are commonly susceptible to enzymatic discoloration. This is the reaction of enzymes or polyphenolic compounds in living cells. This produces a grayish or brownish tone in sapwood. Mineral Discolorations Typically seen in the forms of dark lines or streaks in oak, green or brown patches in sugar maple, or purple to black areas in yellow poplar; mineral discoloration sometimes develops in standing or fallen trees in mineral rich soils. Preventing discolorations caused from iron stain and weathering are quite manageable. If you store wood products outdoors, keep them covered yet ventilated to prevent weathering. Also, keep your ferrous metals from having direct contact with lumber to prevent black ink stains. Other types of black stains and discolorations, like zebra stains, enzymatic discolorations or mineral discolorations, are naturally occurring and challenging to control. PC N provides excellent research papers on wood stain. One paper (51pp), "Wood Discolorations & Their Preventions, with an Emphasis on Bluestain," by FPInnovations™, is accessible at: The NWPCA Industry Marketing Committee is currently developing a marketing piece to outline various types of stains as a valuable customer handout. Stay tuned for further development. Customer Resources

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