Mao: The Unknown Story by Jung Chang, Jon Halliday Illus., maps
another fine book on the black slime itself.
http://www.amazon.com/Mao-Story-Jung-Chang/dp/0679746323/ref=sr_1_1?ie=UTF8&s=books&qid=1283790985&sr=8-1
You can do it by turning off the water.