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BELL SYSTEM TECHNICAL JOURNAL 



seemed to be no reason electrically why wood pulp would not make a suit- 

 able insulating material, and from the mechanical standpoint many of the 

 difficulties involved in wrapping the insulation would be eliminated. 



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Fig. 2 — Comparison of 1212 (left) and 2121 (right) pair cables 



The Development of Pulp Insulation 



Pulp Machine 



The first crude experiments on insulating wire with pulp were done by 

 pouring a suspension of pulp over a wire backed up by a fine mesh screen 

 and after the water was drained away lifting the wire up together with 

 whatever fibers clung to it and then rolling the wire on a flat surface. These 

 samples gave an idea of the type of product to be expected and looked so 

 interesting that a study of equipment and methods was authorized. It 

 developed that the machine most adaptable for our purpose was the stand- 

 ard single cylinder paper machine in use in the paper making industry. 



