This specification applies to black and yellow varnished woven cloth and tape for electrical insulation, having as a base fabric poly(ethylene terephthalate) yarns in the warp direction and glass yarns in the filler direction. Materials needed in the manufacture of cloth and tape include base fabric, filler thread, warp thread, and varnish. The varnished fabric and tape shall be free from wrinkles, blisters, or any imperfections which will detract from its value as electrical insulation. Sheets, rolls, and tapes of black varnished cloth shall have two different types of surface finish: greasy and dry. Yellow varnished cloth shall be furnished only with dry finish. Under normal room conditions greasy tapes shall have the property of sliding freely between layers when moved by the fingers, and shall show a decidedly oily surface. Dry finish tapes shall show some resistance to movement when so handled, but shall not bind or stick together and shall not have an oily surface. A slight amount of waxiness shall be permitted in dry cloth if dullness of surface is not apparent or if noticeable amounts of wax cannot be removed mechanically from the surface. Different tests shall be conducted in order to determine the following electrical and mechanical properties of the cloth and tape: dielectric breakdown voltage, breaking strength, tear resistance, elongation, and temperature index.