Q. We make a lot of wood mouldings out of yellow-poplar. We have received some yellow-poplar with gray stain on the ends of the lumber, running a foot or so up the board. What is this? Does it affect the use of this lumber for moulding or other uses?
A. This stain is sometimes called log end stain, as it occurs when the logs are stored in warm weather prior to sawing into lumber. It is caused by a fungus getting into the ends of the logs as they begin to dry out slightly. In pine and a few other species, this stain can get into the wood around the knots as well. In a few instances, the sapwood can be gray from this fungal infection, from end to end of the lumber. (Gray stain can also result due to oxidation of sugars and starches in the wood.) We can dip the freshly sawn lumber into a fungicide to prevent new stain within the lumber, but logs are not treated this way.
This stain would be a defect for any product used without stain or paint—used “au-natural.” However, almost all Y-P will be painted or stained a darker color, so it will be covered and therefore is not a defect for most users. The stain does not affect the wood quality; the stain is caused by a dark blue colored fungi, so the wood is the same quality and processing will be the same. One exception: With a heavy infestation of the fungi (really dark colors), the porosity of the wood can be slightly increased which can affect finishing.
To accommodate this stain in hardwood lumber, we have the two grades: No.2A Common, which has stain counted as a defect, and No.2B Common, where stain is ignored. Further, for some species, the standard grading rule (which counts stain as a defect) is modified to allow stain without penalty; check the lumber rule book. This all can be really confusing to some people, as oftentimes the buyer does not know the fine details of the grading rules. (For example, in addition to this stain variation, did you know that planed lumber is graded using the better face of the lumber while unplanned lumber is graded from the poorer face?)
Therefore, to avoid any miscommunications between buyer and seller, it is best to add some clarifying comments to the purchase order, such as “stain is a defect” or “light stain is not a defect.” The more restrictions, the higher the price of lumber, so be careful, yet practical. In fact, if you notice any defect (natural or man-made) in your incoming lumber that costs you extra money, consider working with your supplier to fine tune the grades (fine tune incoming lumber quality). This fine-tuning practice, which is encouraged by the NHLA and others, is fairly common…why should you pay for something you cannot use efficiently and profitably?