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BS EN 12150-1BS EN 12600 (Class 1C1)Approved Document KReviewed Technical Specification

Toughened Safety Glass (Tempered)

Thermal pre-stressing engineered for high impact resistance and diced safety fracture.

Engineering Definition: Monolithic float glass subjected to controlled heating to approximately 620°C followed by rapid forced-air quenching, inducing balanced compressive stresses on exterior surfaces and tensile stress within the core (BS EN 12150-1).
Material Construction Matrix

28mm High-Performance Insulating Glass Unit (IGU)

Thermal Transmittance:1.1 W/m²K
Acoustic Reduction:Rw 32 dB
Explode Layers
1
Outer Pane (Surface #1 & #2)(6mm Low-Iron Toughened)
6.0mm
2
Warm-Edge Spacer & Hermetic Seal(Composite Polymer & Butyl)
16.0mm
3
Argon Gas Cavity 90%(Noble Gas Fill)
16.0mm
4
Inner Pane (Surface #3 & #4)(6mm Toughened Low-E Soft Coat)
6.0mm
Physical & Mechanical Performance Characteristics
Safety Class:Class 1C1 (BS EN 12600)
Bending Strength:4 to 5 times stronger in bending than annealed float (characteristic bending strength 120 N/mm²)
Thermal Shock Resistance:Withstands temperature differentials up to 200°C (vs ~40°C for annealed)
Fracture Behaviour:Disintegrates into small, relatively blunt granular dice, drastically reducing laceration risk
Typical U-Value (Ug):5.7 W/m²K (single glazed monolithic) — requires IGU assembly for thermal efficiency
Acoustic Reduction (Rw):Rw 29 dB (4mm) to Rw 35 dB (12mm)
Max Sheet Dimension:Up to 3210mm × 6000mm (jumbo line capacity dependent)
Density & Mass:2.50 kg/m² per 1mm nominal thickness

Key Architectural Advantages

  • •High resistance to human impact and mechanical wind load
  • •High thermal endurance preventing thermal fracture from solar hotspots or proximity to heating units
  • •Compliant safety glazing classification for commercial doors and low-level glazing

Critical Engineering Constraints

  • •CANNOT be cut, drilled, notched, or edged after thermal toughening — all fabrication must precede furnace heating
  • •Susceptible to nickel sulphide (NiS) spontaneous inclusion fracture unless heat soak tested (HST) to BS EN 14179
  • •Zero post-breakage containment when fractured alone (requires lamination for barrier or overhead applications)

Fabrication & Edge Processing Tolerances

Cut After Toughening:PROHIBITED (Catastrophic Fracture)
Heat Soak Testing (HST):Recommended to BS EN 14179

All hole centers must be positioned at least 2× glass thickness from glass edges to prevent stress cracking in furnace.

Architectural Specifier Checklist

Verify these technical criteria prior to contract documentation:

1Confirm all notch, hole, and edge details prior to sign-off (post-toughening modification causes catastrophic shatter).
2Specify Heat Soak Testing (HST to BS EN 14179) for all structural, overhead, or high-level facade installations to mitigate NiS inclusion risk.
3Check visible safety kitemark positioning against framing rebate depth so compliance remains verifiable post-installation.

Frequent Commercial Applications

Frameless Glass Doors & Entrances
Commercial patch-fitted doors with countersunk hinge cut-outs.
Internal Frameless Partitions
Dry-jointed 10mm or 12mm office dividing walls.
Balustrades (Infill Panels)
Fully framed four-edge clamped safety panels.
Network Procurement Routing

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Recommended Action: Direct supply specification for cut-to-size toughened panels or local glazier installation quotes.
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Reviewed by: Chartered Facade Engineer, BuyGlass Technical Editorial Panel
Last Standard Verification: 2026-10-30