Heat Seal Tester The J&B Hot Tack 4000 Tester is the successor of the J&B Hot Tack 3000 Tester and is a highly sophisticated instrument that automatically measures the heat sealing properties of heat sealing packaging materials in an accurately controlled environment. It is the ideal instrument for producers of raw materials, packaging material manufactures, semi-finished material producers and research laboratories. An extensive range of adjustable parameters enables the user to test various materials such as films and coated paper, with options to test cardboard and thicker laminates.