Cover Glass Deep Dive: Soda-lime vs. aluminosilicate - the real difference
Apr 03, 2026
Most people think cover glass is just glass. It is not. The chemistry matters more than most buyers realize.
Soda-lime glass
This is what windows and drinking glasses are made of. Composition: about 70% silica, 15% soda (sodium oxide), 10% lime (calcium oxide). Cheap. Around $0.50 per square meter. But it breaks easily. Surface hardness is about 550 MPa after thermal tempering. The real problem? It scratches at level 5 on Mohs scale. Sand (quartz) is level 7. That is why soda-lime phone screens look terrible after a month in a pocket.
Aluminosilicate glass
Replace some of the soda and lime with alumina (aluminum oxide). Typical composition: 60% silica, 15% alumina, 10% soda, 5% magnesia. Corning Gorilla Glass is aluminosilicate. So is AGC Dragontrail and SCHOTT Xensation. Cost is $3–8 per square meter. Hardness after ion exchange: 650–900 MPa. Scratches at level 6–7 Mohs. Much tougher against sand.
The hidden trade-off
Aluminosilicate is stronger but more brittle. Drop a soda-lime phone from waist height. It might survive. Drop an aluminosilicate phone from the same height. It also might survive. But hit the edge of an aluminosilicate panel against a metal corner? It shatters into sharp shards. Soda-lime cracks but often stays in one piece. That is because aluminosilicate stores more internal stress from ion exchange. Great for drops on flat surfaces. Terrible for point impacts on edges.
What to pick
High-end phones and automotive displays: aluminosilicate. Budget devices and large-format static displays (kiosks, whiteboards): soda-lime is fine. Just know what you are buying.
