Question

give the meaning of do cream and mantle like a standing pond.​

Answer 1

This line means as the cream of the milk is still and does not move and the Standing pond, like that only Gratiano is describing Antonio as he is sad and sitting idle and his visages or face is unchanged ... Gratiano is telling this so that he can make Antonio speak.

Here Cream refers to the white cream of milk and mantle means to stand still like the scum that forms on the surface of a pool