Plasterer washed out pollyfill bucket onto our wall. How to clean it?

[Dan24]

Hi there, would really appreciate some advice on how to clean diluted pollyfiller from my wall (a plasterer washed his bucket out and it splashed against the wall and he refuses to clean it).

The house was built in 1986 and I assume it's reconstituted or cast stone but I'm not certain. Have tried normal soap and water but I'm struggling to have an impact.

 

[yorksbuilder]

Pressure washer should clean it off

 

[^woody^]

Leave it to weather, else you will have a more noticeable clean area of wall.

You could try using a fine wire brush - one that is of brass not steel and with light not heavy brushing, and some white vinegar as that's mildly acidic.

After, splash a bit of milk mixed with dirt (or soot if you have some) there and that will allow algae to grow and tone the area down.