I am eternally fascinated by Takuro Kuwata's work, but I think he's very cagey about his techniques (and I dont blame him).
For example, he says the crackling, thick glazes are feldspar-centric, which I believe, and that he uses pins in the clay to arrest its descent, which I believe, but regarding the gold & mercury colors;
"The gold part is colored by using the same method as European ceramic does, such as handles of Wedge-wood’s cups."
I just dont believe that he's using luster as described. My gut tells me he's using a variation on some Egyptian paste theme where somehow, he forces whatever is responsible for that color to migrate to the surface during firing.