A bath shaker (10) is provided for agitating liquid baths. The bath shaker (10) incorporates a "flexible parallelogram" mode of movement wherein a bath shelf (20) is attached to and supported by two, parallel opposing flexible arms (112). Present on each flexible arm (112) is a first attachment portion (124) sandwichedly held by an upright extension (120) and a first hold plate (110), the arrangement causing the first attachment portion (124) to serve as a flexible hinge. A drive mechanism (16) produces a reciprocating action of the bath shelf (20) through the use of an eccentric (80) and a pivoting lever (46) attached to both the eccentric (80) and the bath shelf (20). The flexible parallelogram arrangement defines the reciprocating motion to be substantially rectilinear and makes for an entirely noiseless mode of travel, while producing an extremely smooth transition between reciprocations. Two bath containers (24) are supported by the bath shelf (20) and are provided with a highly accurate temperature control system (26).