ᐅ Sanding Interior Plaster (Gypsum-Cement): Which Grain Size Should Be Used?

We used an interior plaster of the type Sakret MIP 02 Fine (grain size 0 – 0.8 mm). The surface was troweled, resulting in a very rough texture to the touch (it easily scratches skin on finger joints, etc.) and it also sheds a small amount of sand after drying when you run your hand over it flat.

According to the painter/site manager, sanding off the loose particles is necessary. On site, the painter showed me sanding off with a scraper followed by sweeping. This treatment produced a good surface and the area adjacent to the fully skim-coated precast ceiling has already been treated accordingly; but with over 1000 m³ (35,300 ft³), the process takes a very long time and generates a lot of dust (for a continuous 30 cm (12 inches) band around all walls touching the precast ceiling, the job took about four hours).

Now I want to borrow a long-neck sander with an appropriate vacuum attachment. I could get a professional device from Flex, but the question is which grit of sanding material would create a surface similar to scraping and sweeping?

In the end, the surface will only be painted twice, with no fabric or wallpaper applied. The surface should not be completely smooth and flat like a baby’s bottom but may still have some texture.

Would it be best to start rather coarse (60 grit) and finish with 100 grit for touch-ups?

Before I buy any sanding materials, I wanted to ask you about your experiences with this!

Thank you very much.

In case someone else faces the same question, I'll answer myself:

Tested today. Result with my plaster: grit 80 original flexible abrasive fits and produces a surface similar to scraping and sweeping.

And it’s faster and hardly dusts, especially with extraction. But it’s only moderately enjoyable.