a pedagogic sealing apparatus for seaming thermoplastic layers includes a sealing station and a trimming station . the sealing station includes a movable platen jaw which compresses the layers against a fixed jaw . current flow through a resistance ribbon in the fixed jaw elevates the temperature of the layers to provide a fused seam between the layers . an indicator is provided to apprise the student of the termination of a preselected duration heating pulse and the commencement of a cooling cycle . the platen jaw is heated by a resistance ribbon optionally actuated conjunctively with the fixed jaw ribbon to seal layers which require additional heat to fuse their interface .