Littleton Softening Point

The littleton softening point is the temperature at which the log (viscosity) for a glass is 6.6 Pa/s. This temperature is usually beyond that of typical service for the glass, but needs to be known - especially if firing an enamel or frit onto a glass article – giving an absolute maximum upper temperature limit for processing of the glass.

Measurement is conducted using the international standard ASTM C338 for fibre elongation in which the temperature of the fibre is increased at a standard rate and elongation measured against time. This test gives confidence for operating limits in downstream manufacturing processes, comparison of softening points between glasses without need for full viscosity curves, expert interpretation and advice to help clients understand and use this data.

• ASTM C338-93 Standard Test Method for Softening Point of Glass

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