[There was a subtle clack on the wood as Lupin set his glasses aside, and the others in the room would notice that his dark eyes were lose somewhere deep in his thoughts. He doesn't need to look up the information--its there, and he can't say why.]

Light a flame with the intent to purify dark influences in a circular basin--it doesn't need to be big. Loop the rope in a circle around the flame, and let the flame die on its own accord. The smoke will permeate the material, and that should work. Mostly.