A friend made a pair of earrings in wax and had them cast in gold. They
turned out so well that she decided to have a mold made of one of them.The
mold came out fine, but the gold earring used for the mold was several
shades darker than it was originally, and did not match with its mate. She
tried polishing it, pickling it, …nothing worked. What is the reason
this happened, and what, if anything, can she do to restore it to its
original shade, which she prefers to the darker hue?