Smoked oil patina

About the smoked oil patina, I mistakenly called it ‘burned oil
patina’ in a previous message, the effect I am trying to get is
similar to the one in Joe Wood’s (sorry Joe) jewelry which has
a mottled white and black surface. Is there some one out there
who might suggest where I could start with doing experiments in
an attempt to get a similar effect. I am not trying to copy his
work just get white and black mottled surface colors one two of
my pieces. thanks in advance!! Sharron fron sunny Saigon