If you have to do this often, investing in an ionic cleaner would be
worth it. It removes LOS in less than a minute and leaves it shiny
white, without damaging pearls nearby. Torching it, even gently,
cannot be done as safely (to the piece) -- there's sill a dull, gray
finish (which may be what some people like). When I receive back
pieces that are badly tarnished from galleries, I clean them with my
ionic cleaner and then re-patina based on what seems to be selling.