Here's a link to the sculpture and multimedia classes, which include assemblage and welding
http://www.mfa.org/search/programs?solrsort=sort_date+asc&filters=event_type%3A%22Studio+Art+Class%22+studio_art_sub%3AOther
http://www.mfa.org/search/programs?solrsort=sort_date+asc&filters=event_type%3A%22Studio+Art+Class%22+studio_art_sub%3AOther