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The workshop abuts fencing that has been treated with a copper preservative. The fencing has a green mold or fungus on the fence board sides. It has a black fungus on the fence board and post ends that are exposed directly to the rain. While the lignins in the ends have obviously been removed from the weathered ends; there is no visible spotting on the fence boards / posts. There are also diseased cherry trees on the property that I have not bothered to cut down and burn. Article was interesting.

I use a hot water bath only for bending these thin <= 1/8" veneers. The water bath temperature is 127 deg F to 145 deg F and a clean bath is used on each day's new bending. If I am doing multi-species bends it is birdseye Maple then Maple then oak then walnut then cherry. I do so because it is reputed that cherry will stain other woods; although I have not observed this. The oxalic acid bath is about two tablespoons per five gallons of water. Woods may be kept in the water bath 20 minutes to 2 hours or longer. While the copper deposits show up within hours or less, the red coloration may take a week or longer to develop. I only notice the coloration once the wood is dry. The coloration can not be sanded out of the wood, although it does not completely penetrate a 1/16" veneer. The coloration darkens over time. When the stronger 3% solution of oxalic acid is applied to dry wood to remove the metal spotting, the red color may or may not appear. Although that could be due to how thorough I rinse the wood. The workshop is a high dust environment with many different wood species. This winter the bentwoods are taking longer (2-3 days) to dry to 11-15% moisture. As a result I have been seeing green mold on the bent boxes. Exposure to light, air movement, and sanding gets rid of the mold - still its a pain.

I am a Shaker box maker. I hot water bend cherry, walnut, and maple woods. The hot water bath has oxalic acid added to prevent metal spotting. Upon occasion cherry and even less frequently my birdseye maple bands will develop a pink splotching. It looks remarkably like your spalted hemlock bowl. While the splotching is generally irregular in shape, it sometimes appears to be almost straight lined across the grain. If I do get metal spotting I use a 3% solution of oxalic acid to remove the metal spotting then rinse with clean tap water. I would say that 90% of the coloration comes when I use this 3% oxalic acid solution. It takes the pink color 10 days or more to develop and will continue to develop color even under a 5 coat nitrocellulose lacquer. Do you think I have staining or spalting? Do you have any possible cures for either? I can sell spalting not staining.

Since I have tried everything a chemist could think of to remove staining I am leaning towards spalting. Especially since I have found this pink color on birdseye maple. My guess is that the 3% oxalic acid is promoting the spalting.