INSULATION OF WIRE WITH PAPER PULP 



91 



minute the polishers are rotated at 5000 r.p.m. to give satisfactory in- 

 sulation. 



Drying of the Insulation 



The method of drying the insulation is very important. In the early 

 experiments low-temperature air drying, high-temperature air drying and 

 finally moderate-temperature-controlled humidity drying were studied. 



Wire and pulp from presses 



A temperature of about 180°F. and 20% humidity was finally adopted. 

 For a number of years this method was used for experimental cables but it 

 was impossible to get electrostatic capacities below .095 mf. per mi. With 

 such values it appeared that the use of pulp would be strictly limited to 

 certain sizes of wire and certain cables. Study indicated that lack of 

 porosity and close adhesion of the pulp to the wire were large factors in this 

 diflEiculty and steps were taken to determine what could be done to improve 



