Removing White Efflorescence Powder From Outdoor Retaining Wall

Unlike mold, efflorescence is harmless – but no more fun to look at. Learn how to prevent this mineral buildup, and, when prevention isn't possible, how to clean it from surfaces.

LESLIE: Now we’re going over to Eunice in Arkansas who has a retaining wall that thinks it’s a chameleon. It’s changing colors. What’s going on?

EUNICE: Part of it is – the part that’s turning white powdery-looking is the part that’s exposed to the weather. And it’s kind of spreading. It looks like it’s – the whole thing will eventually turn white. I don’t know if it’s oxidizing or if moisture from the ground is making it change colors or what.

TOM: You know, that’s exactly what’s happening, Eunice. The white growth is called efflorescence. And essentially, water from the ground pulls up because those concrete blocks are very hydroscopic. So it – water pulls up and then as the water evaporates, it leaves its mineral salts behind. And that’s what that whitish/grayish deposit is.

So it’s not harmful; it’s really just cosmetic. And there’s not going to be a lot you can do to stop it, though, short of removing the moisture – which obviously isn’t possible outdoors.

EUNICE: Oh, OK. So power-washing it or using a chemical or anything wouldn’t make a difference?

TOM: Well, really, all you need – I’ll give you a little trick of the trade for getting rid of efflorescence. If you use white vinegar – so if you were to mix up some white vinegar and mix it with water in a pump-up sprayer, that will melt the mineral salts right away.

EUNICE: OK. Very good. Thank you so much.

TOM: Eunice, good luck with that project. You’re very welcome.