The basic knowledge of chemical strengthening for cover glass
Jun 18, 2026
What's the chemical strengthen working principle? It replaces smaller sodium ions(Na) in glass surface with larger potassium ions(K) under a molten potassium nitrate bath. This kind of "ion exchange" makes a compresssive stress layer on glass surface: Just like to put the glass in a tight jacket, which makes it much harder from crack or scratch.
Compare to untreated glass, chemical strengthen glass can be 3-4 times more impact resistance.
The performance is defined by two key metrics:
Compressive Stress (CS) - defines scratch resistance
Depth of Layer (DOL) - defines drop resistance
Process parameters matter:
Temperature typically runs 350°C–450°C
Longer or hotter treatments increase DOL but may reduce CS due to stress relaxation
Today's innovations are pushing toward precision engineering:
Zone-specific strengthening for uneven-thickness glass (UFG) – bending areas need different treatment than flat areas
Two-step deep strengthening (DDS) – first builds a deep stress foundation, and then adds a high-stress surface layer. The result: better drop and impact performance than standard strengthened glass.
