Best solution for washing painted walls, prior to repainting

[Red Devil]

Hi all

I had just repainted the bedroom walls 18 months prior to doing some DIY work on the landing walls, ceiling and stairways. The fine dust from the black lime seems to have entered the bedroom and really engrained on the bedroom walls. I know that I should have sealed the doors better, but it did not look too bad at first.

I have tried using sugar soap to clean the walls, but no amount of elbow grease seems to shift it. I appreciate that I will have to repaint it, but I would like to clean it up as best as possible before proceeding

Any suggestions as how to clean the walls ?

Thanks for any help

Con

[Weatherlawyer]

You've tried an Hoover?

[Red Devil]

Not tried a hoover. Don't think it would be any good as the dirt seems to be embedded in the paint. It all happened many months ago, but I have just found some spare time to tackle the problem The problem is made worse looking as the walls are a light cream colour, and if you really scrub a small square, it really demonstrates how much dirt is actually on the wall.

[Stuart Noble]

Sugar soap is alkaline, so you could try a weak acid, like vinegar. Not sure what the black dust might be but soot and most black particles are more soluble/dispersible in acid. If you have any "dishwasher rinse", try that on a small patch. Makes the glasses sparkle and is surprisingly acidic

[MB]

Hoovering won't do it, I suspect. The cause is more likely a chemical reaction due to the semi-volatile organic compounds in the paint. It was unknown before 1995, and not every wall paint contains SVOCs. If you Google "SVOC" plus "magic dust" plus "fogging," you'll learn more about it than you'll ever want to know. I recall newspaper stories years ago about fogging, and the only solution mentioned was to use another paint.

Typical of fogging is the appearance of black dust up to 18 months, even two years after you've painted and, typically, you painted in the summer, and fogging first appeared in the heating period. I tried to find some links for you, but as I'm in Germany, most of the links I found (there are hundreds of them) are in German. Here's one you can read that explains the problem: