Treating to Inhibit Blue Stain
December 6, 2009
Question
I have about 2000' of prime shortleaf pine to dry. My go-to kiln guy is out of business, so it'll have to start as air dried. Former kiln guy remembers there being some sort of compound you can spray on the lumber to inhibit staining, but couldn't remember the name of it. Anyone know of such a chemical? Past experience with air drying in the Spring here in NC Arkansas has always rewarded me with blue boards. Any advice is appreciated.
Forum Responses
(Sawing and Drying Forum)
From Professor Gene Wengert, forum technical advisor:
There are a variety of approved chemicals, including NP-1, Busan 1009 and others made by Buckman Laboratories.
From contributor T:
My grandpa taught me years ago how they used to do this. I recently found an article on this online from a magazine dated 1921, "The Timberman," called "Dipping Lumber to Prevent Stain."
From Professor Gene Wengert, forum technical advisor:
Because of the caustic nature of these chemicals on lumber, we no longer use them.
From contributor K:
Is good stickering and full air circulation the solution? I am in the cold desert and not the humid south. Air drying works like a charm. If I had to mill premium material and could not tolerate any risk of blue or sticker stain, is there something I could spray on before I air dried? Also, "caustic nature on lumber" - is the structural integrity of the wood compromised?
From Professor Gene Wengert, forum technical advisor:
For blue stain to be active, the temperature must be 50 F, although up to 90 F is faster; there must be moisture (over 22% MC, but wetter than that is better); there must be oxygen; and there must be food (sugars in the sapwood). Eliminate one of these four and you control blue stain. In most cases, we dry the surface fast enough to eliminate water. When one of the four cannot be eliminated for sure, then we poison the food supply. Fungi certainly require a specific pH for activity, so if we change the pH (such as by making the surface caustic or high in pH), then we can also control the fungal activity.
There are several chemicals that can be applied by spraying, and these are approved for application upon wood. Incidentally, none of these control molds really well; to control mold requires a strong chemical and that is risky and may require one to be licensed to apply it.
