The W.A. Baum calibrated tube is an integral part of every Baum instrument. Made of glass to produce a tube that is optically clear, smooth, easy to clean, dimensionally stable and has very little affinity for mercury. Several layers of strong, crystal clear Mylar film that strengthens the tube and maintains its structural integrity even if the inner glass is broken enhance all Baum glass cartridge tubes.
The bore of Baum tube is 5 mm to prevent separation of mercury, which can cause erroneous readings. Ceramic graduation marks are fused to the glass for permanence and the entire tube is carefully annealed to eliminate both longitudinal and ring strain.
The ends of the tube are flame glazed to prevent chipping. Tooled collars fit precisely in tube sockets.