What is this frothy substance that comes up between cracks on painted floors, painted on concrete?

Question

I have this house. the floors are concrete floors, painted. The house was left empty for a year and a half. (Long story.) When I returned to the house last weekend, one room, the floor was covered with white frothy specks, and a few actually looked like shaving cream. obviously it isn't. what is it, and what is the best way of eliminating this? I'm afraid it might be mildew, and if i swept it, spores would come flying up into the air.

any tips/advice?

thanks.

Answer 1

It is caused by water under the floor. You could check the drainage away from the house and water in the area.

Answer 2

Effervescence, it is caused by water infiltration.

Answer 3

Rod, I think you mean efflorescence.

Yours sounds like the non destructive variety, and it's caused by the unbound salts leeching out of cementitious materials, and shouldn't worry you. You can just wash it off. If you like you can paint the walls with a coat of masonry paint or other waterproofing coating to seal them, but you should be OK just cleaning off, and over painting with your usual paint, if you want to.

Here's a link describing it, with photos.

http://en.wikipedia.org/wiki/Efflorescen...