Insurance case when help is provided by friends

I hope someone can help us or tell us if it makes sense for our friends to report the following case to their insurance. We had friends over who were helping us with the interior construction of our new single-family house. One friend sprayed a solution on the walls with a spray device (I am now unsure what it is called), the windows were not fully masked off yet. To our dismay, we later saw that there were spots from the spray mist all over the windows. Despite intensive cleaning efforts, the spots cannot be removed. Really annoying with the huge panoramic windows. Do we have a chance to get the damage reimbursed by the helper’s liability insurance?

That sounds like a favor damage. (Friend helps with moving for free and something breaks) The friends' personal liability insurance should cover it. In your case, it is not the "phone fell down" case with great potential for abuse, but really just bad luck. Asking doesn't cost anything.

I just checked again, Clima Silikatgrund was used. Maybe someone still has a tip on how to get rid of this stuff.

Try using a so-called "Schmutzradierer". These are used damp. These things really work wonders in some cases. They only cost a few cents.. so the attempt costs almost nothing.

Hello, it is not without reason stated for the product: "Note! All surfaces that are not to be painted such as glass, ceramic, clinker, etc. must be well covered." Unfortunately, I fear for you that the product chemically reacts with glass :-(

The ingredients are highly alkaline, the glass is etched.