Description
Enviro-Lite HS Heat Strengthened Glass is produced similarly to Enviro-Lite FT Tempered Glass, except that the annealed glass is heated to a slightly lower temperature of 620o C, and volume and pressure of the cooling process is less rapid. As a result in Enviro-Lite HS Heat Strengthened Glass having a residual surface compressive level between 3,500psi but less than 10,000psi, or edge compression greater than 5,000psi but less than 9,700psi. When broken, the appearance of the break pattern will vary widely depending on the amount of compression. Enviro-Lite HS Heat Strengthened Glass is typically produced at the desirable range of 4,000psi to 7,000psi. The break pattern is relatively large, the fragments tend to remain on the glazing, and the strength is sufficient.
Enviro-Lite HS Heat Strengthened Glass is only twice the mechanical and thermal strength of annealed glass, and like Enviro-Lite FT Tempered Glass, Enviro-Lite HS Heat Strengthened Glass also retains most of its physical and chemical properties. The only physical property that changes is the bending strength.
Heat strengthened glass has smaller optical distortion and is less prone to spontaneous breakages, and such strongly recommends that Enviro-Lite HS Heat Strengthened Glass be used for curtain walls and windows glass application. Even though the distortion levels for heat strengthened glass are lower, it is important to minimize this reflected image distortion caused by the contract of the glass with roller in the furnace. These distortion levels are most apparent when the heat strengthened glass are eventually processed into Enviro-Shield Solar Control Reflective Performance Glass or Enviro-Shield Low E Heat Control High Performance Glass. During the heat strengthening process, the orientation of the glass in the furnace should be such that the horizontal glass dimension is parallel to the roller wave, and also during installation the glass are installed in the same orientation. To assist our customers with this problem, AGS imprints the Enviro-Lite HS logo on the bottom right corner of each lite of glass.
In some cases, local building codes or additional strength to resist high wind load is required, and then Enviro-Lite FT Tempered glass should be considered.
Types Available
Enviro-Lite HS Heat Strengthened Glass is available in a wide range of glass types in varying thickness and includes the following:
- Clear and tinted glass
- Pattern Obscure
- Enviro-Shield Reflective Glass
- Pyrolithic Reflective Glass
- Pyrolithic Low Emissivity Glass
- Screen Printed Glass
Handling Precaution
Heat Strengthened glass cannot be cut or drilled after tempering. Any alterations after tempering such as edges grinding, sandblasting or acid etching may reduce the thickness of the compressive layer, thus reducing its strength, and can cause premature failure.
A strain pattern, or sometimes referred to as irridescene, sometimes visible under the certain lighting conditions and when viewed at certain angles. This strain pattern is inherent in the tempering process and should not be considered a defect.
Prone to spontaneous fracture. Spontaneous fracture is a result of internal inclusions, such as nickel sulfide, which can be found in the glass as a result of the float glass manufacturing process. Though heat soaking of tempered glass can be used to control the breakage, it cannot eliminate such spontaneous fracture.
The thermal tempering process does not increase surface resistance to scratching or abrasion compared to ordinary glass.
