Q: Is there any kind of a chemical that can be used to detect the presence of antifungal dip in the loads that we receive? Currently, we require that our vendors dip their loads of white oak and red oak and we're running into stain issues. We'd like to know whether or not they are, so we can process the undipped ones first to preserve them and also to file complaints.
 
 
A: The dipping process that you refer to is done to green lumber at the sawmill. The lumber is immersed briefly in a mixture of chemicals. Some of the chemicals remain on the lumber's surface and provide an insecticide and fungicide barrier on the lumber's surface to prevent new infestation. Most fungal damage is done to the sapwood by a blue-colored fungus. Hence, the stain is called blue stain or sap stain.
 
Yes, indeed, the companies that supply the chemicals for dipping wood do have tests for the presence their chemicals. Each chemical dip will have a different test procedure, so when buying from several mills, it will be tough to test for dipping unless they're all using the same chemical for dipping.
 

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However, the dipping only prevents fungal stains. Most often in oak, the blue or grayish stain in the sapwood is caused by the enzymatic oxidation of sugars in the sap. (I believe that this is what you are dealing with.) Sometimes these are called gray stain, sap stain, oxidation stain, enzyme stain or chemical stain. Sticker stain or sticker shadow is in the same classification. So is pinking and browning in hard maple and a few other species.
 
These stains aren't controlled by dipping in a fungicide. They can be bleached away, and some dips do have a bleaching effect on the lumber's surface, so the stain may only show up after planing. These stains begin to develop in the log while it's stored in warm weather, so old logs are much more likely to develop this stain in the lumber during drying. In warm weather, the stain can begin to develop within 24 hours. This makes it extremely hard to control. Years ago, this stain in gum lumber was prevented by steaming the lumber prior to drying. I've also recently seen a patented heating process that apparently deactivates the enzyme in fresh oak lumber and thereby prevents the stain.

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