Many times clouds can be seen hovering just above the liquid surface in a cup of hot coffee. The above picture approximates their appearance.

It is tempting to think that the coffee clouds are akin to those in cloud chambers. One can see occasional rapid cloud clearing streaks. This seems to suggest some kind of interaction betweem something in the air (passing thru the air?) with the suspended cloud droplets. If anybody knows the nature of these rapid wake like phenomena, please drop the author a note, and the info will be incorporated on this page. [Added 13 March 2005.]

It might be an interesting science fair project to find out under what conditions the clouds can exist. Variables to consider might include (but are not limited to):
(1) Temperature of coffee
(2) Temperature of surrounding air
(3) Humidity of surrounding air
(4) Electrical polarity of liquid (plus/minus/neutral) - (this could get sophisticated)
(5) Electrical conductivity of coffee (use salt to increase conductivity)
(6) Cup material - insulating (ceramic) or conductive (metallic)

Items four, five, and six are listed because, according to Dr. Mahmoud Melehy of the University of Conneticut at Storrs, water fog droplets (above lakes and ponds, etc.) are suspended in the air by an electrical effect similar to that in Millikan's Oil Drop Experiment. [Link no longer works.]