Finish Problems and Solutions – BLACK DOTS
BLACK DOTS CAUSE Common causes for black dots include iron filings that react with tannins and water, as on an oak floor finished with water-based urethane, and leave black stains. The filings can come from sharpening scrapers or a sander hitting a nail or a heating duct boot. Tannins alone can create dots, found at the end of a capillary tube in the wood. Mold can also leave black dots. FIX Avoid problems with iron filings by not sharpening scrapers over the floor...
