Cleaning artificial stone

Hello, in our new building the window sills are made of light artificial stone. Although we took care during construction and taped off the window sills, we can't get them properly clean. In some areas, they have a matte surface. Do you have any experience or ideas on how or with what to best clean them?

Thank you.

Hello,

you have to be extremely careful with this stone, we have the artificial stone as a windowsill and as an open staircase in our house. Water stains remain visible forever and the stone scratches very easily. We even have scratches on the staircase, although we only walk around here in slippers and socks. By the way, our neighbors do too... There is a polish that removes superficial scratches. Ask your windowsill installer about it, we also got it from our staircase builder.

What should one imagine under [Kunststein]?

asks Yvonne with holiday greetings