Marshmallows that have been heated to glowing with a blow torch will spark when subsequently heated in a microwave oven.  This curious behavior has also been observed when various wood-containing objects are heated with a blow torch and then microwaved.  It is known that conductors can spark when heated in a microwave oven.  Therefore, it is proposed that some carbon in the wood and marshmallow is converted to graphite when heated to very high temperatures.  Infrared spectra of and conductivity measurements on the surface of the ashes formed provide evidence to support this idea.  These simple experiments provide an interesting way to demonstrate to students that carbon is contained in various materials.

Possible graphite formation on organic material

246th National Meeting (2013)

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