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BLUE STAIN DISCOLORATION |
IRON STAIN DISCOLORATION |
WEATHERED
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It is important to understand that not all discoloration on lumber is the result of mold that poses a risk to human health. Timber staining, such as Blue Stain, is an example of a type of naturally occuring fungus that grows in many species of hardwoods. Blue stain, which is typically blue to grey in color (but can be red, brown, black, and even yellow) is not detrimental to human health, nor does it effect the integrity of the lumber itself. While not always making for the most attractive of pallets, it poses no threat to you or your products when used. The ability to identify timber staining over mold can go a long way in avoiding unnecessary delays and keeping a positive relationship with your customers and suppliers.
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Like blue stain, iron staining is not dangerous to human health nor damaging to the integrity of the lumber. Iron staining occurs when moisture bridges the gap between natural extracts in the wood and introduced metals such as fasteners, straps, brackets, and saw blades. The wetter the wood, the greater the chance of and the surface area covered by the iron stain. Oak, being one of the strongest and most readily available hardwoods for the pallet industry, is high in tannin extracts and therefore one of the more susceptible species to iron stain.
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Weathering (aka sun bleaching) occurs as a result of prolonged exposure to the sun and moisture. The UV rays, given off by the sun, change the color of most lumber to a greyish hue. While this is merely a cosmetic discoloration and has no ill effects on the stability or integrity of the lumber, it is important to note that pallets that are built with weathered boards or become weathered after being built will tend to have a rougher surface, as shown above, that freshly built pallets.
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