Surface Tension of Various Molten Glasses*

A bstract Surface‐tension measurements were made on a series of molten glasses at 1200° and 1350°C, using the maximum bubble‐pressure method. A base glass was chosen with the composition of 17.4% Na 2 O, 10.1% CaO, 72.5% SiO 2 , or 1.4 Na 2 O: 0.9 CaO:6.0 SiO 2 , to which 0.030 gram‐atom of various elements in the form of their oxides was added. An increase in surface tension was produced by Li, Si, Ca, Ra, Mn, Ni, Co, Fe, Zn, Al, Mg, Ce, and Zr. A decrease was produced by Ti, Na, B, K, Pb, and V. The values at 1200°C ranged from 235 dynes per centimeter for the glass containing vanadium, to 320 dynes per centimeter for the zirconium‐containing glass; the base glass had a value of 304 dynes per centimeter. The surface‐tension values at 1350°C were generally slightly less. Surface‐tension results for various analyzed commercial glasses are given also for temperatures of 1200° and 1350°C.