Strange localized mold problem
I live on Vancouver island, which is a pretty moist place. Our house is free of mold except for our dining room table. It is about 100 years old, I think made from walnut, and unfinished on the underside. Every couple of years it develops quite extensive bluish mold on the underside. No other piece of furniture gets it.
The house has a slab as the finished floor. the only thing I can think that is unique to the table (beyond its age), is that it sits on a synthetic area rug – the only piece of furniture that does.
Any insights appreciated.
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Have you tried measuring the humidity level in the room where the table is located?
No I haven't. It probably mirrors the conditions in the rest of the house as the downstairs is essentially one large room. What puzzles me is that the north-facing windows, the rest of the furniture and the walls etc, all show no signs of the mold. What small amounts of mold we sometimes get on window tracks and inside the dishwasher is the typical black variety. This is a very distinct blue colour - more like I'd expect to find outside in the rain forests here.
Could it be a fungus endemic to that wood which has bloom cycles? Have you turned off the lights to inspect for bio-luminescence? There is blue stain (sap stain) fungus which has tricked me into thinking someone spray-painted in the woods. I've only seen it on pretty decayed wood.
I suggest going to your local big box store and buying two or three inexpensive humidity monitors. (It is sometimes sold as a greenhouse Rh monitor.) These units aren't super accurate but will indicate if your indoor humidity levels are too high.
If your humidity levels are normal, you could then clean and seal the underside of the table without having to worry about a larger air-quality issue. I did a quick search and found several articles online for handling mold on old wood. It seems to be a fairly common issue.
I'll try that and see. The Concrobium should encapsulate the mold, but if not next summer I'll coat the whole underside in polyurethane.
There is a good chance it is what you describe. Unfortunately it's too late to check for bio-luminescence, as I've wiped all the mold (fungus?) off and coated the affected surfaces with Concrobium.