According to Wookieepedia, the the props are made of wood.
Also, due to the brittleness of the stunt blades used during this fight, which were little more than wooden dowels, Diamond was forced to instruct Alec Guinness and David Prowse to stop their blades before contact due to their fragility.
If there isn't any particularly special feature about the props to separate them from the rest of the image, were they done manually?
How were the lightsaber effects accomplished?
I'm interested in all the movies, but mainly episode IV/original trilogy.