ZIP BLACK GRATE & BARBECUE POLISH This black grate polish is for polishing black iron. This traditional wax-based graphite black polish, that gives a brilliant silver-black finish to cast iron. Good for restoring rusty or tired looking fireplaces, grates, BBQ and other cast iron metal. Apply evenly with a cloth or brush and leave to almost dry before removing excess. Allow to dry fully for a matt black finish. For a Shiny finish simply polish thoroughly once dry with a soft dry cloth or brush.