But, to answer your original question, it would take as few as one weighing, but no more than 4, to determine the heavy piston.

 

Grayhawk

Scott and others,

 

Hmmm....Do we know what the tolerance of an individual piston is? If for instance it were even .05 gram, the difference between the combined mass of two groups of 13 could be as great as 1.3 gram, resulting in many more ounces of beer consumption before the 624 gram piston is found.

 

Rob