Viscosity of Recent Container Glass*

A bstract A high‐temperature, concentric cylinder viscometer has been constructed and calibrated. The calibration checks within 1% that obtained by Lillie for a similar apparatus and provides further evidence of the high degree of reliability of this type of measurement. The contention of Washburn and Shelton that the calibration in such instruments is a function of the viscosity is shown to be false. Because four independent investigations have been unable to check this contention, it may now be regarded as spurious. A medium temperature‐range fiber viscometer for measuring the viscosity of glass in the annealing range has also been constructed. It is shown that the Fulcher equation, log η=− A + B / T − T 0 , fits the data obtained on the two instruments to within 0.5% for commercial soda‐lime glasses. Complete viscosity data as a function of temperature are given for sixteen commercial container glasses, and the analyses are also included. These glasses show a wide range of viscosity.