Q: I have some quartersawn white oak lumber with light-colored spots where every sticker was located, instead of having dark marks like regular sticker stain. What causes this
A: This defect is called reverse sticker stain or reverse sticker shadow. The difference between stain and shadow is primarily whether you are selling or buying.
The speed of drying determines the color of the wood, especially when the logs have been stored too long in warm weather. I suspect, therefore, you have lumber from old logs.
Next, stain or color variations develop very early in drying - usually above 40 percent moisture content. Plus, slower drying means darker colors in the wood than does faster drying. So, we need to look for variations in drying rates that occurred very early in drying. What could cause the wood under the stickers to dry faster than the wood between the stickers?
I would guess that two things happened when you first got the lumber on sticks. You probably had some very dry stickers that were used to stack the wood. These stickers then quickly dried the wood that they were in contact with, resulting in light colors. If the rest of the lumber were also dried quickly, then it too would have been light in color. But, I suspect that after stacking, the lumber was put outside for "a short time" and got rained on or was exposed to very slow drying. This resulted in slow drying between the stickers and darker colors in those areas. Because exposure to rain is usually just on the upper side of the lumber, you might notice that the "reverse sticker stain" is mainly on one side of the lumber.
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