Fiber Elongation to check Annealing and Strain Point of Glass ASTM C336

Fiber Elongation to check Annealing and Strain Point of Glass ASTM C336

ASTM C336 is used to measure the viscosity of the glass and provides valuable data about the strain points, annealing points, and setting thresholds for seals. It was proposed that the viscosities at the strain point and annealing point should be 1014.50 and 1013.00 poises respectively at 4°C temperature. Viscosity is expressed in poises.


    By calculating the viscous elongation rate of the fiber of the given glass, using ASTM C336, the annealing and strain points of the glass can be determined. ASTM C336-71 provides information on developing an appropriate annealing schedule, stress release estimation, and estimation of setting points for seals.

    Test Procedure:

    ASTM C336 takes place in a specialized furnace made up of the copper core, and glass fiber is attached. After the formation of glass at a high temperature, it is cooled carefully, typically at 4°C. The size and diameter of the given sample are measured. The following factors are evaluated while assessing the strain and annealing points; choice of glass, optical lever adjustment, temperature correction, fiber support, cooling rate, sample length, expansion, and viscosity.

    Specimen Size : 

    The specimen size can be up to 6 cm in length.


    The viscosities are calculated by using the following formula


    where η is the viscosity (poise), L denotes effective fibre length (cm), mg represents suspended force (dynes), d denotes fibre diameter (cm) and e is the elongation rate (cm/sec).


    Core Materials Testing Services


    A variety of microscopy and spectroscopy tools available for precise measurements from the nano to the meter scale.

    Metrology Testing Services


    TEM SIMS Profilometry

    Materials Testing

    ASTM and ISO standard and custom chemical, mechanical, thermal, corrosion tests, etc. for all materials metals, ceramic or polymers.

    Materials Testing Services


    Nondestructive Testing Electrical Testing Chemistry Analysis

    Product Testing

    Thousands of tests for product quality and reliability under heat, humidity, temperature shock, vibration, drop, electrostatic discharge.

    Product Testing Services


    Vibration Testing Humidity Testing Accelerated Aging

    Looking for Material Testing?

    We have 500+ Material Test already Done for top companies

      Send us a request

        idea icon

        Want to connect with an expert before you leave?