I once jury-rigged blackout curtains by attempting to dye regular white curtains with a navy dye; the colour only partially took, and turned out to be at precis

I once jury-rigged blackout curtains by attempting to dye regular white curtains with a navy dye; the colour only partially took, and turned out to be at precisely the right spot on the em spectrum to act as an irresistible magnet for bees, which would consistently wake me on summer mornings coming though the open window and buzzing against the botched curtains, rather obviating the purpose!