There may be a number of things, or combination of, that caused the molding and mildewing: 1) Pollen in the air. 2) Dust in the air. The shop garage is pretty dusty dirty. 3) No or poor ventilation. I think this was a major factor. The surface o f the lumber stayed damp too long. I've had old salvaged lumber mold and m ildew because of surface dampness. 4) This time of year for milling the boards, despite the tree having falle n during the winter months (it's best to fell a tree during the winter and best to mill a green log during the winter, but good ventilation would have countered these "negatives"). 5) Bill (SonomaProducts), being envious, came over and sabotaged the board s.
I hand-washed each board, again, with a 1:3 Clorox/water solution, sticker/ stacked them and, now, have a fan blowing over them. The mold and mildew w ashed off pretty easily, so I don't think there will be any permanent disco loring (or tatooing, as I call it) of the boards, but I'll keep an eye on t hem. One smaller board (a "scab" board, cut from the side of the log) was most exposed and had already began to warp/cup.
For comparison, two years ago, when the walnut was milled, I was able to st icker/stack the boards, in a permanent place, immediately after cleaning. I had a fan blowing over them, for the first month of drying, as well. Ye sterday, I removed these walnut boards and there was no mold or mildew, at all. The milling, cleaning and stacking of these boards were done in mid-w inter. *Yesterday, I removed them from storage because it's time to start sizing them up, for making the trestle table, to hopefully be completed for the farm/camp hunting season.
In general, you never know when problems will arise, with lumber as this. Hand washing the boards was no fun.
Here's some pics of yesterday's pecan and walnut: https://www.flickr.com/p hotos/43836144@N04/?details=1
Yesterday, I also restacked some of the pine flooring, we had been planing. The shop has been too crowded, with all these projects scattered about. I'm getting sick and tired of stacking and restacking lumber, especially t he big lumber. Sometimes, it ain't no fun, anymore.