Michael Dresdner

straight talk about wood finishing

I sanded my floors with an orbital sander…

Q: I sanded my floors with an orbital sander and completed four rooms with no problems. There were some dark water spots on the floor. I used Clorox bleach to lighten the water spots and washed the chlorine as directed. I allowed the floor to dry for two days and removed any dust that might have accumulated. This morning I applied the waterbased satin clear. As I went over the water spots, the finish caked up and appeared almost like hard wax.
I don’t know what caused the problem, which also occurred on some other areas of the floor. Is the something I could do to smooth the area over the water spots or another bleaching agent that I should use?

A: For future reference, the best way to remove watermarks from raw wood is with oxalic acid. Still, laundry bleach usually does not create problems with waterbased finishes. However, laundry bleach reduces to water and salt when it dries. It’s not common, but excess amounts of salt in the wood could cause waterbased finish to go haywire.
I’m not sure what you meant by other areas, but if the same thing happened in areas that were not bleached, we can discount the bleach as the culprit. Waterbased finish that behaves the way you described, setting to a wax instead of a film, can also be caused by high humidity. In addition, there are other contaminants that could be responsible, but without a lot more information, I could not tell you exactly what they are in your case. Your best bet is to start over; go back down to the bare wood, scrub with TSP in water to remove any salt or grease residues, then when the floor is dry and lightly resanded, add one coat of Zinsser SealCoat, a clear primer, before applying the waterbased floor finish.