The report describes a test in which aluminum cans recovered from municipal waste, together with known amounts of contaminant, were processed by a 'zig-zag' vertical air classifier to remove aerodynamically light contaminant. Twelve test runs were conducted; the proportions of contaminant were varied and machine performance observed. For each run, the two output streams of the air classifier were analyzed to find the amount of aluminum cans and contaminant reporting to lights and heavies. The efficiency of the machine was found to vary with contaminant loading and air flow rate. Results of these analyses, a description of the equipment under test, and a discussion of econmic factor which pertain to the use of this device in an aluminum recovery system are included in this report.