According to ASTM standard C148-17, it provides 2 different kinds of testing methods to evaluate the quality of annealing. These test methods can be used in the quality control of glass containers or other products made of similar glass compositions, where the degree of annealing must be verified to ensure quality products.
Testing method A applies to measure retardation less than 150nm, while Test Method B is used in determining retardation less than 565nm. A polarimeter is introduced in Test Method B. Our Polarimeter model PSV-413 is designed based on Test Method B. A quarterwave plate with an optical retardation of 141nm is inserted between the specimen.
When examining bottom of cylindrical containers, make sure the viewing field is at maximum darkness by setting the rotating scale to zero position . Then pull the selecting lever to choose Sensitive Color Method . Under this method , the tint plate is placed in position. Rotate the container to determine the location which has the highest order retardation color. Next pull the selecting lever to choose Senarmont Method. A darkened cross will appear in the container bottom,while lightened areas can be seen between the darkened legs of the cross. Rotating the analyzer causes the darkened extinction cross to separate into two darkened arcs. When determining the retardation at a selected point , rotate the analyzer until the blue-gray color is just displaced by the brownish color at the selected point. Finally convert the rotation angle of the analyzer to the apparent temper number as follows:
Apparent Temper Number | Analyzer Rotation Angle(°) |
1 | 0.0–7.3 |
2 | 7.4–14.5 |
3 | 14.6–21.8 |
4 | 21.9–29.0 |
5 | 29.1–36.3 |
6 | 36.4–43.6 |
7 | 43.7–50.8 |
8 | 50.9–58.1 |
9 | 58.2–65.4 |
10 | 65.5–72.6 |
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