Aluminosilicate and Chemically Strengthened Glass
Aluminosilicate glasses replace much of the lime and boron of ordinary glass with 10–25 % alumina, which stiffens the network, raises the softening point by 100–200 °C and — in the alkali-containing versions — lets potassium ions be swapped for sodium at the surface to build 700–900 MPa of compressive stress. That ion-exchange step is what makes Gorilla Glass and Dragontrail survive drops at 0.5 mm thick. The same chemistry, drawn as fibre, gives E-Glass, S-Glass and C-Glass, the reinforcement in most fibreglass laminates.
Popular aluminosilicate glass grades
Compare in the explorer| Grade | Yield, MPa | Tensile, MPa | Density, g/cm³ | Machinability | Weldability | Best for |
|---|---|---|---|---|---|---|
| Gorilla Glass | 700 | 350 | 2.42 | Not recommended | Not recommended | Chemically strengthened thin display covers |
| E-Glass | — | 3,400 | 2.58 | Poor | — | General-purpose reinforcing fibre and PCB cloth |
| S-Glass | — | 4,890 | 2.49 | Not recommended | — | High-strength fibre for aerospace laminates |
| C-Glass | — | 3,300 | 2.52 | Not recommended | — | Acid-resistant surfacing veils and mats |
All 4 aluminosilicate glass grades
Choose aluminosilicate glass for
Thin cover glass for displays, touch panels, cameras and sensors that must survive drops and pocket abrasion; instrument windows and faceplates under 2 mm; lamp and halogen envelopes and high-temperature sight glasses to about 700 °C; and glass-fibre reinforcement — E-Glass for general laminates and circuit boards, S-Glass for high-strength composites, C-Glass for corrosion-resistant surfacing.
Look elsewhere when
The pane is large or thick and only needs to be strong (tempered Soda-Lime costs a fraction as much), the part is a lab, process or optical component (Borofloat 33, N-BK7), it must be scratch-proof against sand and steel (Sapphire — chemically strengthened glass is still glass at Vickers 600–700), it will be cut or drilled after strengthening (finish first, or use a glass that can be machined as-is), or the fibre laminate needs the stiffness of carbon (Carbon Fiber composites).
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Aluminosilicate glass by application
- Display and device covers
- Gorilla Glass at 0.5–1.1 mm for handheld and wearable screens, 1.1–2 mm for automotive, kiosk and industrial displays; cut, edge-polish and drill before the ion-exchange bath, and optically bond to the panel afterwards.
- Sensor and camera windows
- Gorilla Glass discs and squares where a thin, drop-tolerant window is needed and the abrasive is fingers and fabric; move to Sapphire when sand, keys or steel will touch the surface.
- Reinforcing fibre for composites
- E-Glass roving, cloth and mat for hand-layup, infusion, pultrusion and FR-4 circuit boards; S-Glass unidirectional tape and cloth for spars, pressure vessels and armor backing where strength-to-weight must beat E-Glass by a third.
- Corrosion-resistant laminate skins
- C-Glass veil as the resin-rich surface layer of chemical tanks, pipes and scrubbers, protecting an E-Glass structural laminate behind it from acid attack.
Working with aluminosilicate glass
- Melting & forming
- Cover glass is fusion-drawn (overflow) into sheet 0.3–2 mm thick with pristine, untouched surfaces, then cut to blanks; fibre is drawn through platinum-alloy bushings at about 1,200 °C into 5–24 µm filaments and sized for the resin system. Bulk aluminosilicate for lamps is drawn as tubing at higher temperature than borosilicate — working point around 1,200 °C or more.
- Cutting & grinding
- Blanks are CNC-ground, drilled and edge-polished with diamond tooling, or laser-cut for thin sheet, entirely before strengthening; the polished edge sets the drop performance because failures start at edge flaws. After ion exchange, no cutting or drilling — the compressive skin (30–100 µm deep) would be breached and the part fails.
- Strengthening & bonding
- Ion exchange runs in a potassium-nitrate bath at 380–450 °C for several hours, building 700–900 MPa surface compression to a depth of 40–100 µm; the part comes out flat and with no dimensional change worth measuring. Covers are then coated (anti-fingerprint, anti-reflection, ink borders) and bonded to displays with optically clear adhesive or laminated. Fibre is bonded by its sizing to epoxy, polyester or vinyl-ester resin.
- Tolerances & design rules
- Sheet thickness ±0.05 mm, outline ±0.1 mm, edge chamfer or 2.5D polish specified on the drawing. Keep holes at least one thickness from edges and radius corners at 1 mm or more. Design stress for chemically strengthened glass can be several times that of annealed glass (retained strength depends on damage depth versus compression depth); for fibre laminates design on fibre volume fraction and layup, not on the fibre number alone.
Other glass series
Aluminosilicate and Chemically Strengthened Glass — frequently asked
What is aluminosilicate glass?
Aluminosilicate glasses replace much of the lime and boron of ordinary glass with 10–25 % alumina, which stiffens the network, raises the softening point by 100–200 °C and — in the alkali-containing versions — lets potassium ions be swapped for sodium at the surface to build 700–900 MPa of compressive stress. That ion-exchange step is what makes Gorilla Glass and Dragontrail survive drops at 0.5 mm thick. The same chemistry, drawn as fibre, gives E-Glass, S-Glass and C-Glass, the reinforcement in most fibreglass laminates.
Which grade of aluminosilicate glass should I use?
Gorilla Glass (or an equivalent alkali-aluminosilicate cover glass) for any thin transparent cover that will be dropped, scratched or flexed — device screens, instrument and automotive displays, camera and sensor windows, protective faceplates — in 0.4–2 mm sheet, chemically strengthened after cutting. E-Glass when the requirement is fibre reinforcement for laminates, pultrusions and PCB substrates: 3,400 MPa fibre tensile strength, 72 GPa modulus, low alkali for electrical grade. S-Glass for the 30–40 % stiffer and stronger fibre (about 4,600 MPa, 87 GPa) in aerospace, ballistic and pressure-vessel laminates where carbon is too brittle or too costly. C-Glass for surfacing veils and mats in contact with acids, where its chemical durability beats E-Glass.
Which grade of aluminosilicate glass is easiest to machine?
E-Glass (machinability poor, 15/100), then C-Glass (12/100).
Chemically strengthened or thermally tempered glass?
Thermal tempering needs the glass to be thick enough (about 3 mm or more) for the quench to build 70–120 MPa of surface compression, and it distorts thin sheet. Chemical (ion-exchange) strengthening works on sheet down to 0.3 mm, builds 700–900 MPa of compression in a shallow layer without distortion, and is the only route for display covers. It is more expensive per square metre and its shallow layer can be scratched through, so it suits thin covers rather than doors and shelves, where tempered Soda-Lime remains the right answer.
E-Glass or S-Glass for a composite part?
E-Glass is the default: 3,400 MPa fibre strength, 72 GPa modulus, low cost, excellent electrical properties and every weave and format available, so it carries most boat hulls, tanks, panels and FR-4 boards. S-Glass (S-2 glass, a magnesium aluminosilicate) is about 35 % stronger (4,600 MPa) and 20 % stiffer (87 GPa), keeps strength better at 300 °C and in fatigue, and costs several times more, so it is reserved for aerospace parts, pressure vessels, ballistic panels and springs. Between them in performance and price, and often the better answer for stiffness, is a carbon–glass hybrid layup.