When the lights are bright in the main room and dark in the blue room, the reflected image cannot be seen. When the lighting in the blue room is increased, often with the main room lights dimming to make the effect more pronounced, the reflection becomes visible and the objects within the blue/hidden room seem to appear, from thin air, in the space visible to the audience. A common variation uses two blue/hidden rooms -- (one behind the glass in the main room, and one to the side) -- the contents of which can be switched between 'visible' and 'invisible' states by manipulating the lighting therein.