a first vibration generator positioned against the first container wall so that, when the first vibration generator is activated, vibrations including a first selected frequency are produced by the first vibration generator and pass into the chemical bath liquid contained in {HEAD ~ the container} at {TAIL ~ the first container wall}; and 
at
a first vibration generator positioned against the first container wall so that , when the first vibration generator is activated , vibrations including a first selected frequency are produced by the first vibration generator and pass into the chemical bath liquid contained in { HEAD ~ the container } at { TAIL ~ the first container wall } ; and
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