Volume Resistivity

Volume Resistivity is the ratio of direct voltage applied to the electrodes to that portion of current between them that is distributed through the volume of the specimen.

Surface resistance is the ratio of the direct voltage applied to the electrodes to that portion of the current between them which is in a thin layer of moisture or other semi-conducting material that may be deposited on the surface.

High volume and surface resistance are desirable in order to limit the current leakage of the conductor which is being insulated. ASTM D-257. Based on "Standard Tests on Plastics/Bulletin GlC: 4th Edition," published by Celanese Plastics Co., Division of Celanese Corp., Newark, N. J.