In glass manufacturing, selecting the right strengthening method-Thermal Tempering (Physical) or Chemical Strengthening-is critical to achieving the required structural and optical performance for your application. While both processes induce compressive stress to enhance strength, their mechanics, workable thicknesses, and post-processing capabilities differ significantly.
1. Post-Processing & Machining Flexibility
Thermal Tempering: Once glass undergoes thermal tempering, no further mechanical processing is possible. Any attempt to cut, drill holes, or grind edges will instantly release the internal tension, causing the entire sheet to shatter into tiny granules.
Chemical Strengthening: Chemically strengthened glass can technically undergo light post-machining. However, machining cuts directly through the thin surface compressive stress layer ($\sim 10–25\,\mu\text{m}$), exposing the untreated inner core. This localized damage disrupts surface stress uniformity and severely reduces overall mechanical strength. Therefore, complete fabrication before chemical strengthening remains the industry best practice.
2. Thickness Thresholds: The 2mm Rule
The choice between thermal and chemical strengthening is heavily dictated by glass thickness:
Sub-2mm Ultra-Thin Glass: Chemical Strengthening Is Superior
For glass under 2mm, thermal tempering is impractical; rapid air quenching causes severe surface warping or thermal breakage. Chemical strengthening is the definitive choice for sub-2mm glass because:
Zero Optical Distortion: The process occurs in a static 400-500 degrees molten salt bath below the softening point, ensuring 100% surface flatness.
Superior Relative Strength: In ultra-thin glass, the surface compressive stress layer represents a higher percentage of total thickness. For standard soda-lime glass under 2mm, chemical strengthening yields 350–500 MPa of surface stress-delivering 3 to 4 times the strength of physical tempering (~90–120 MPa).
Over 2mm Glass: Thermal Tempering Is Recommended
For glass thicker than 2mm (such as architectural panels, glass doors, or heavy industrial covers), thermal tempering is the preferred and cost-effective solution. Thick glass easily establishes the steep thermal gradient required for wind quenching, producing reliable safety glass that fractures into harmless, blunt particles upon failure.
