**Homogenization of tempered glass does not eliminate the possibility of spontaneous breakage.**

**1. Main Causes of Spontaneous Breakage in Tempered Glass:**

- **First:** Spontaneous breakage caused by visible defects in the glass, such as sand grains, stones, bubbles, inclusions, chipped edges, cracks, scratches, etc.

- **Second:** Spontaneous breakage caused by volume expansion due to phase transformation of nickel sulfide (NiS) impurities within the glass.

**2. Nickel sulfide (NiS), as non-glassy particulate matter, is the primary cause of spontaneous breakage in tempered glass.**  

Nickel sulfide is introduced into the glass through impurities in raw materials (e.g., quartz sand, silica powder). Over time, some nickel sulfide particles undergo a crystal structure transformation from the α-phase to the β-phase. During this transformation, the volume of the nickel sulfide particles expands significantly. This expansion generates intense internal stress within the tempered glass, leading to spontaneous breakage.

**3. Homogenization treatment (also known as heat soak treatment), which involves reheating and annealing tempered glass, is widely recognized as an effective method to address spontaneous breakage.**  

Tempered glass is reheated to approximately **290–300°C** and held at that temperature for a specified period before being slowly cooled. This process allows nickel sulfide particles within the glass to complete their phase transformation during homogenization, causing potentially problematic glass to break in a controlled factory environment.  

This method **significantly reduces the post-production spontaneous breakage rate**, improves product yield, and minimizes the impacts of breakage on transportation, installation, and subsequent reprocessing.