A Party Trick for when the wine is flowing... A good trick to try on a group of drunken scientists HOW TO DO THE TRICK Explain that just as a glass prism splits up the different colours of white light, when different coloured light passes through glass, it is also affected to an extent that depends on its colour. Write the words CARBON DIOXIDE on a piece of paper, CARBON in red and DIOXIDE in blue. Put the paper close behind the stem of a wine glass, and look at the words through the stem. The red letters turn upside down, but the blue ones don't. So is the glass affecting the red light more than the blue?