ᐅ Insurance Claims When Receiving Help from Friends

I hope someone can help us or advise whether it makes sense for our friends to report the following case to their insurance.

We had friends over helping us with the interior fit-out of our new single-family house. One friend sprayed some kind of solution onto the walls using a spray device (I’m not sure what it’s called), but the windows were not fully masked off yet. To our dismay, we later noticed spots from the spray mist all over the windows. Despite extensive cleaning efforts, the spots cannot be removed. This is very frustrating, especially with the huge panoramic windows.

Do we have a chance of getting compensation for the damage from the helper’s liability insurance?

That sounds like a favor damage.
(A friend helps with the move free of charge and something gets broken)
This should be covered by the friends’ personal liability insurance.
In your case, it’s not a typical "phone dropped" situation with high potential for misuse, but just genuinely unfortunate.
Asking doesn’t cost anything.

I just checked again, and Clima Silikatgrund was used. Maybe someone has a tip on how to remove this stuff after all.

Try using a so-called "magic eraser." These are applied damp. In some cases, they really work wonders. They only cost a few cents, so it’s almost free to give it a try.

Hello, it’s no coincidence that the product states:
"Attention! All surfaces that are not to be painted, such as glass, ceramics, clinker bricks, etc., must be well covered."
Unfortunately, I fear this product chemically reacts with glass :-(

The ingredients are highly alkaline, causing the glass to be etched.