The chance occurrence of the Raku means that no two pieces are alike.
Raku is rapidly fired until glowing hot (1000C). It's then taken from the kiln whilst still glowing and placed in a container of wood shavings and sawdust. These instantly combust and the flames inside the container consume the oxygen causing the clay and the glaze to react. This reduction draws the metal in the glaze up to the surface, creating the rich iridescent colours found on Chris' pots.
Due to the complicated colouring of each vase, the images seen will not be an exact likeness.