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Glass Transition Temperature - GTTM

This test procedure was employed in the Foresight Ceramic Database and now is available for those having an account at Insight-Live.com. Accumulating test data using the variables defined in these procedures enables us to create tools that enable you to compare the physical properties of materials and recipes.


This is quoted for ceramic frits and is derived from the graph produced by a dilatometer. The line (representing increasing thermal expansion) climbs steeply as temperature increases. When the transition point is reached an inflection (direction change) in the curve occurs, after this the expansion increases more rapidly until the material reaches the softening point. That point is the peak of the curve, after that the line drops off vertically and melting proceeds.

This is equal to the sintering point in the HMA test.


TP - Value (V)

Value in degrees: e.g. 560C

Simple dilatometric curve produced by a dilatometer

Simple dilatometric curve produced by a dilatometer

Dialometric chart produced by a dilatometer. The curve represents the increase in thermal expansion that occurs as a glass is heated. Changes in the direction of the curve are interpreted as the transformation (or transition) temperature, set point and softening point (often quoted on frit data sheets). When the thermal expansion of a material is quoted as one number (on a data sheet), it is derived from this chart. Since the chart is almost never a straight line one can appreciate that the number is only an approximation of the thermal expansion profile of the material.

Out Bound Links

In Bound Links

  • (Tests - Related test) HMA - Heating Microscope Analysis for Frits
  • (Project) Frits

    The number of different frits in the world can be intimidating, there are thousands. However, unlike stains, their are a wide range of standard formulations that have been made for many years. We are ...

By Tony Hansen

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