The Art of Sealing Base Metals Through Glass

Methods are described by which base metals may be sealed to and through glass, even though the metal and glass have different coefficients of thermal expansion. The method consists in providing a large surface of contact between the glass and the metal, and in so proportioning the metal that the stresses resulting from the difference in coefficients of expansion are less than the ultimate strength of the joint between glass and metal. Four different types of seals are discussed: First, the flattened wire seal for small electrical conductors. Second, the ribbon seal for special purposes. Third, the disk seal for commercial manufacture of seals for carrying currents of the order of 100 amperes. Fourth, the tube seal in which metal and glass tubing are joined together.