Why is the skin of the old bronze seal red?
The loss of zinc. The redness of the skin of the old bronze seal is caused by the loss of zinc after contact with acid and alkali in the soil. Copper is a metal element and a transition element, with chemical symbol Cu, English copper and atomic number 29. Pure copper is a kind of soft metal. When it is just cut, its surface is reddish-orange with metallic luster, and its simple substance is purplish red.