Niello

In the early medieval period a black enamel called 'niello' was frequently used to decorate relief work. Niello is unfortunately rather toxic, but there are various simple substitutes which look the part and won’t kill you!

The easiest way of decorating relief work is to paint black nail varnish over the metal and then wipe away the excess so that it only covers the grooves and areas of low relief. Black enamel paint mixed with glue will have the same effect, as will detonating a stink bomb (!) in a bag or box with the items to be nielloed.