I have witnessed copyists unashamedly applying antique finishes to their products on Cat Street in Hong Kong and in The Panjiayuan market in Beijing. There are shops in Curio City which clearly offer fakes for resale. This is no secret. It is as though the word "antique" and "ancient" is a contraction for "antique style" or "ancient style."

But hydrofluoric acid, as Rosanna mentions, needs to be in a controlled environment. And I have heard horror stories from those who buy and sell it.

Just Fred