We painted my wall two times already first was a dark blue and some white powdery stuff was spreading after the paint dried, now we painted it again now in purple and it still has the white stuff when dried.

This is a picture that I took left side is the dry one and right side I sprayed water on it that's how it should look like but this white stuff keeps coming back when driedenter image description here

Other pictures enter image description here

  • 3
    What is the wall made of?
    – Tester101
    Sep 28, 2015 at 12:12
  • 3
    Looks like efflorescence coming out of a concrete wall. What kind of paint did you use? Is this a basement wall?
    – iLikeDirt
    Sep 28, 2015 at 12:57
  • 1
    Did you use ammonia or TSP to clean the walls before you painted? before
    – ojait
    Sep 28, 2015 at 15:03
  • 1
    Yeah, what kind of paint are you using and on what surface? Did you use a primer first?
    – paulmz
    Sep 28, 2015 at 16:53
  • 1
    If you paid (a professional?) to have the walls painted, contact them to correct the issue. Were both coats professionally applied? A real pro would know what type of paint to use for any given surface. You should, at least, work to get a refund on this botched paint job.
    – paulmz
    Sep 29, 2015 at 13:46

2 Answers 2


That would be efflorescence on a concrete wall. Efflorescence is when water passes through the wall and evaporates on the surface. The minerals contained within the water can't evaporate, so they stick around, usually looking like a fine white powder on the surface. You can see the same thing with hard water that evaporates from a kitchen sink. It's not harmful to the wall, but it is ugly and will eventually ruin the paint, because the paint is likely impermeable to moisture (if it is acrylic, latex, alkyd, or oil-based), so it will bubble and peel over time as the water in the wall tries to escape.

The root cause is moisture movement through the wall, or, simply put, the wall getting wet. To prevent this, keep the wall from getting wet. Typically this is the job of the roof, but the wall itself can have its own protections. If the wall is simply a monolithic concrete slab with no finishing on the outside, that would contribute to the problem too. Broadly, what you want to do is to keep water out of the wall's core while letting water already there escape to the exterior side.

The cheapest solution would be to paint the exterior side of the wall with a breathable, vapor-permeable paint (e.g. a silicate mineral paint--NOT a typical paint!). The more complete and permanent solution would be to cover the exterior side of the wall with some type of breathable, vapor-permeable weather barrier substance (e.g. liquid-applied water-resistive barrier material, housewrap, asphalt-soaked paper) and then put up bricks or some other decorative covering.

  • Thanks but is there any alternative besides painting over it again? Maybe a cleaning product or something that will help permanently prevent this? I don't know the exact product.. Oct 1, 2015 at 1:33
  • If I'm right, the only thing that will permanently prevent it is stopping water from entering the wall--probably from the outside. Once water is inside the wall, it's going to come out and cause efflorescence.
    – iLikeDirt
    Oct 1, 2015 at 1:43

I agree with I like dirts' instructions. The only way you might be able to make the inside wall stop producing dust is to paint first with a concrete paint. Dryloc is a popular brand and it can be tinted to the final color. If possible wait for the ground or wall to dry a bit. What this masonry paint does is penetrate the concrete somewhat and when it dries becomes a non-permeable barrier to the water. But don't expect miracles. The best way is to excavate the outside wall, apply a petroleum tar based waterproofing, install perforated drain pipe on a stone base, grade the soil away from the foundation and install gutters and downspouts.

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