Glass Strengthening
SPECIALGLASS by two routes — physical (thermal) tempering and chemical (ion-exchange) strengthening — and matches the method to what the part actually needs. Thick architectural and safety glass gets thermal tempering; thin cover glass, precision optics, and parts with cutouts get ion exchange. One raises strength fast and cheap on simple panels; the other builds far higher strength on thin and complex parts without touching their flatness or clarity.
Two Methods, Two Jobs
The two processes strengthen glass by opposite mechanisms, and that difference decides where each one wins.
Physical tempering heats glass to 620–680 °C and quenches the surface in seconds. The surface cools and locks into compression while the core stays hot — putting stress through the full thickness. It’s fast, low-cost, and improves thermal stability, but the rapid handling limits it to relatively simple shapes and a thickness floor around 3 mm. The right choice for thick safety and architectural glass.
Chemical strengthening submerges glass in a molten potassium-salt bath at 300–450 °C for hours, exchanging surface sodium ions for larger potassium ions to build a deep compressive layer. It reaches far higher surface compression, works on glass as thin as 0.5 mm, holds complex outlines and cutouts, and leaves transmittance and flatness essentially unchanged — at a higher cost. The right choice for thin cover glass, precision optics, and shaped parts.
Method Comparison
| Physical Tempering | Chemical Strengthening | |
|---|---|---|
| Process temperature | 620–680 °C | 300–450 °C |
| Processing time | Minutes (rapid heat & quench) | Hours (set by target strength) |
| Thickness range | 3–19 mm (typical) | 0.5–5 mm (typical) |
| Strength increase | 4–5× annealed glass | 6–8× annealed glass |
| Surface compression (CS) | >69 MPa (10,000 psi) | >600 MPa typical, up to >900 MPa |
| Depth of layer (DOL) | N/A (stress through thickness) | >15 µm, up to >50 µm |
| Edge compression (EC) | >67 MPa (measured separately) | N/A |
| Shape limitations | Relatively simple shapes | Complex shapes & cutouts allowed |
| Thermal stability | Improved | No significant change |
| Surface quality | Good | Excellent |
| Cost | Low | High |
Choosing the Right Route
The decision comes down to thickness, shape, and what has to stay stable. For thick, simply-shaped panels that need to meet a safety code and resist thermal stress — tempering delivers it fast and cheap. For thin glass, tight cutouts, or optics that must stay flat and clear under load, ion exchange is the only route that reaches the strength without distorting the part. When a program spans both — a thick frame and a thin cover — we run each on the process that fits.
Need Help?
Send glass type, thickness, size, hole/print requirements, and certification needs for a tempering quotation.