”Has anyone any proof that moisture in the form of vapor can move extractives in wood? I have never heard this and have been told before that humidity alone will not move extractives...liquid water is required.”
Water liquid is the primary cause of extractive migration, but water vapor can also be a source. Check out the first paragraph in the section on water-soluble extractive bleed in this document - Understanding Extractive Bleed
”If indeed this problem is due to high humidity, I would expect to see and hear of other issues, such as a warped door, or the cracks between the drawer fronts getting small. The gap between the doors looks substantial indeed, so I am tempted to discount humidity. Further, with high humidity at a closet, the bathroom would be a mold factory. Further, this is not the first DF door on the Island, so why haven't we heard of this before?”
In the theory I proposed, I ruled out warpage because doors and drawer faces usually have a stable substrate so they stay flat. I suspect mold/mildew is a concern in Hawaii in the same way it is in Florida and residents have to take the same preventive measures .
”Why is there the coloration on all four edges? What do all four edges have that the faces do not have? If moisture is moving in the edges, wouldn't also eventually move in the faces? ”
The discoloration on all 4 edges is really odd. The only explanation I could think of is that moisture is entering the wood more readily at the corners where the finish is thinnest. It literally looks like each edge of the doors and drawer faces were set in a pan of water and allowed to soak it up for a time. Over time, I’d expect to see the entire face of the doors & drawers turn the darker color.
”Why is there a small circle darkening near the hardware on the door? Is there something under this spot that is different than the adjacent areas? ”
Is this the spot you’re looking at?
It looks like moisture has traveled through the wood to that spot – there seem to be streaks of color between the larger dark area above and the round spot below. I wonder if the moisture is traveling between the wood and adhesive…(if it’s moisture at all)?
”Why is this darkening not seen where the hardware is located? Even if the hardware restricts moisture movement, we should not see such a sharp demarcation? The only difference appears to be that there is no finishing under the hardware...were the doors finished in place and then the hardware was installed?
Note that the area around the hardware on the door is darkened. The hardware did not seem to slow the reaction. If the reaction were moisture related, the hardware would seem to be likely to slow the moisture movement. ”
The wood covered by the hardware has not changed color and is still very light. This is a normal condition… the lignin in wood is photoxidative and changes color with exposure to sunlight (UV). I’m theorizing that the extractives migrating to the surface of the wood are causing the darker color compared to the color of the wood in the center of the door/drawer.
”If this is a reaction between the adhesive and the finish, if we examined the glue line at the edge and then near the center, we will see a difference in thickness, especially with a thinner glue line in the center. Less adhesive should mean less chance for a reaction. ”
I considered that the discoloration might be caused by some component (e.g., plasticizer) of the adhesive migrating to the surface of the wood or possibly off-gassing from the core (it looks like the door has a foam core). But I thought it was less likely that the color change was caused by the adhesive or core because the doors and drawer fronts are so different are were provided by different fabricators.
Moving forward, I would investigate these potential sources;
Find out what adhesives were used on the doors and drawers to see if the chemistry is similar.
After several days of high humidity, measure the MC of the dark and light colored areas on the doors and drawers.
Monitor the dark areas to see if they are indeed expanding and determine the rate.
It’s an intriguing problem and it would be great to define the root cause. Phil has an interesting job!
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(NOTE: Login is not required to post)Mystery Discoloration of Doug Fir Veneer
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