Finishing compound is a polish and protectant for the metal surfaces of a stained glass project. It should be the last item done on a piece before it is finished, unless it needs to be sealed for outdoor exposure. It tends to come in thick gel or paste forms and is rubbed on then polished off. Some finishing compounds are made from carnauba wax.

Enough finishing compound to last through many, many stained glass projects runs between $8 and $12.