Remove plaster residues from sandstone

Who built this wall? I would even guess that the wrong mortar was used.

Who built this wall? I would even guess that the wrong mortar was used.

I think so too. That looks more like efflorescence. The only solution is demolition and rebuilding with the correct mortar. If at all.

These are not efflorescences. The joints were filled with mortar that was too wet and no attention was paid. When grouting, the mortar is usually mixed to a soil-moist consistency, then applied, and then you go over it with a hand broom and done.

This cement haze is very difficult to remove. I would first try water, a stiff brush, and maybe then carefully a high-pressure cleaner. Depending on the situation, also use a sanding sponge. This will improve it but not make it good and clean. You can try many things, but you can only try that yourself. Cement haze remover can also help, but please be careful and targeted. If nothing helps after the first cleaning and the visual standard is high, get yourself a glaze. We always make them ourselves: KEIM Farben for example has glazes. But you should have a bit of a feel for color.

Who built this wall? I would even guess that the wrong mortar was used.

It was a landscaper who apparently doesn't know much about masonry!!

Who usually carries out such work cleanly and neatly? A bricklayer? If you know someone who works in the Pforzheim area (Karlsruhe - Stuttgart), please get in touch!!!

The veil does not come off with the pressure washer.

There are special joint operations and a bricklayer should be able to manage that as well. But if the wall was just freshly built like this, I would ask the operation for a solution...