Darkfield Lighting

We were recently shown an advanced technique for lighting glass objects in the studio; Darkfield Lighting.
This is where a softbox is used directly behind the object, however the area of that softbox directly behind the glass is covered by a black cloth to stop all of the light. This also works to give the black background for the object. The bare strips either side of the blacked out part of the softbox are left to light the glass, this works to just highlight the edge of the glass.