Glass Surface Tension Tester (Filament Contraction Method)

The instrument determines the surface tension of glass in its softening range by suspending a glass filament of specified length and diameter in a vertical tube furnace at a controlled temperature. As the local section of the filament is heated, it first elongates due to thermal expansion, then softens and contracts under surface tension to form an olive-shaped node.

When equilibrium is reached between the surface tension of the softened section and the weight of the lower filament, the node stops growing; by measuring the weight of the lower filament, the surface tension at the hold temperature is calculated. The system is designed for surface tension testing and analysis of glass and glass fibers in research and education settings, with programmable temperature control and precise thermal uniformity.