New and revised British standard specifications

A Specification for insulating boards and tubes made from paper or paper-pulp treated with synthetic resin and bonded together under the influence of heat and pressure was issued in 1929 as British Standard Specification No. 316. That specification was, however, limited to Grade 11 material, which is suitable for use on oil-immersed apparatus and on low-voltage apparatus working in air in dry situations. For certain purposes, however, such as the insulation of apparatus working in humid atmospheres, and for the production of components by machining operations, a different grade of the same class of material is required, and this (higher) grade is now covered by the recently-issued B.S. Specification for Grade I Synthetic-resin Bonded-paper Sheets for Electrical Purposes (B.S.S. No. 547–1934). Grade I material is distinguished from Grade II material by low water absorption, high resistivity, low dielectric loss and good machining properties. It is known commercially under such trade names as pascolin, tufuol, bakelite, etc., and is used extensively for the insulation of telephone switch-boards, armature wedges, terminal strips, armature tooth supports, etc.