How to measure temper number of glass container with a Polariscope ?

The polariscope is a professional tool widely used in the manufacturing and quality control of glass containers. Among them, measuring the temper number of glass containers is one of the important applications. The higher the temper number, the lower the strength and heat resistance of the glass container. For some special commodities, the temper number will also affect the safety and quality of goods.

Measuring the temper number of a glass container requires certain professional knowledge and skills. The following is the detailed measuring method :
1. Prepare the polariscope and place the glass container to be measured at the predetermined position.
2. Rotate the glass container to the desired position so that darkened extinction cross appear.

3. Rotate the analyzer causes the darkened extinction cross to separate into two darkened arcs, moving outward in opposite directions toward the inside knuckle of the container. As the two arcs move outward, they develop a blue-gray color on the concave side and a brownish color on the convex side of each arc.
4. When determining the retardation at a selected area, rotate the analyzer until the blue-gray color is just displaced by the brownish color .
5. At this time, read the angle to which the analyzer is rotated and call it the Temper Number of glass container.

For example , we get above rotating angle 9.5°, it means temper number of this water glass is 2.

It should be noted that any impurities and signs of wear inside the glass container will affect the accuracy of the temper number. Therefore, in order to ensure accuracy, the surface of the glass container need to be cleaned before measurement.

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