A test tube is smashed with a hammer and the pieces are poured into a clear container of glycerine. Then, due to magic or the similar refraction indices of glass and glycerine, the broken pieces of glass disappear and a previously-invisible, intact test tube is removed from the container.

Make sure the unbroken test tubes are near the bottom of the container and that have been rested there for a while to ensure invisibility from far away distances.

PIRA DCS 6A40.30