Highly Polished wire????

Here's one for all those Mat Science gurus..
OK we have all read this... "polished to a mirror finish to further reduced surface impurities.... Polished with what?

Seems like the cure worse than the disease? Wouldn't you introduce more impurities by polishing with a foreign substance. What's the secret formula to remove "impurities" without introducing new ones???

Is it just marketing hype?

- Dan