How to tell if glass is tempered?

To determine whether a glass product has been heated, you can start from the following aspects:
1. Observe the appearance characteristics
Stress streaks: Glass products that have been tempered will have colored streaks observed under polarized light, which is a characteristic manifestation of stress distribution.
Surface flatness: Heating treatment may cause slight deformation of the glass surface, such as the glass surface becoming uneven and not as flat as before.
 Mouth treatment: If the formed glassware is heated to remove the cap, the mouth will be smoother and have no obvious burrs.
2. Check the logo and instructions
 Product labels: Many glass products will clearly indicate whether they have been specially heated, such as "tempered glass" and "heat treated".
Instructions: The product manual usually details the material, processing technology and precautions of the glass, from which you can understand whether it has been heated.
3. Test performance
Heat resistance test: Heat the glass product in a microwave oven and observe its reaction. Glass products that have been heat-resistant, such as borosilicate glass, can withstand higher temperatures without breaking.
Strength test: Tempered glass has a higher impact strength, which can be initially judged by tapping the glass to listen to the sound or observing its impact resistance. Tempered glass sounds crisper and is not easy to break.
In short, the treated glass will have significantly different characteristics from the original glass material. Through the above methods, it is possible to more accurately judge whether the glass product has been heat-treated.