How to check the appearance quality of tempered glass?

Tempered glass has better properties than ordinary glass but is not immune to many of its possible cosmetic defects. The appearance quality problems of tempered glass are widespread, especially the quality problems caused by the tempering process. This article will discuss the appearance quality problems that may arise during the tempering process.

Waviness Defects

One of the most common appearance quality issues of tempered glass is waviness. This defect refers to the glass surface appearing wavy, with many spots visible to the naked eye or unevenness felt when touching the surface. Several factors, including uneven heating during the tempering process or inadequate cooling, can cause waviness.

Waviness Defects

The central part is gray

Gray discoloration on the surface of tempered glass can occur in the area that comes into contact with the roller table during production. This can negatively affect the transparency of the glass, particularly in the central part. There are two leading reasons for this issue: first, the temperature of the roller in the heating furnace may be too high; and second, excessive use of SO₂ gas as a protective gas for the glass can cause gray discoloration on the surface.

Excessive stress spots

Stress spots will appear in tempered glass produced by physical tempering methods, which is determined by the production principle of physical tempering and is also unavoidable. Sometimes this phenomenon is also used to identify whether the glass is tempered. Still, when the stress spots are too heavy, especially when viewed under specific light conditions, appearance quality defects become a problem.

Excessive stress spots

Iridescence phenomenon

The iridescence phenomenon of tempered glass is an optical phenomenon. The iridescent phenomenon of tempered glass is related to the quality of float glass as the original glass and the tempering process.

Iridescence phenomenon

White mist

There is a white mist on the glass; an imprint that cannot be removed is in the middle. The abrasion of the surface of the glass causes the white fog phenomenon of tempered glass. Usually, this wear is caused by friction between the lower surface of the glass and the roller table during processing.

White mist

Scratch

Scratches on the surface of tempered glass are another appearance quality issue that can affect its mechanical strength. Scratches can destroy the uniform stress distribution on the glass surface, decreasing its mechanical strength. Scratches can occur during transportation, handling, or processing.

Scratch

Pitting

The pitting phenomenon is also a kind of appearance quality defect of tempered glass, which can usually be divided into two types: one is intensive, usually pitting is more concentrated, and the appearance of dense pitting is generally due to the heating time too long, or the heating temperature is too high. The other is the scattered type. The appearance of scattered pitting is generally caused by the unclean surface of the loading table, the roller table, or the dirty roller table under the air grille.

pitting phenomenon

Aside from defects that can occur during processing, tempered glass can also exhibit appearance quality problems caused by defects in the float glass. Common defects include point defects such as bubbles, inclusions, and optical deformation.

In conclusion, a comprehensive understanding of the appearance quality issues with tempered glass is necessary to identify and solve problems effectively. It’s important to note that some quality problems can have multiple causes, requiring a thorough analysis to address them adequately. While most appearance quality issues do not directly impact the safety performance of tempered glass, a high-quality product should meet general quality requirements. At VSOM GLASS, we strive for zero product defects while meeting safety performance requirements and avoiding potential appearance quality issues. This ensures our products meet technical standards and fulfill our customers’ design requirements.