How do I remove concrete from window frames?

Question

We had the house re rendered and the concrete has gotten on the frames of the windows, which are white, any idea on how to remove the grey concrete without damaging the white surround

Answer 1

Muriatic acid will dessolve the concrete.

Answer 2

Use a 50/50 ration of acid to water and saturate spots, should soften enough to wipe off, also use a plastic putty knife to help.  Work carefully as to not scratch the glass.

Answer 3

sledgehammer