What is the primary safety difference between toughened and laminated glass?

Toughened glass shatters into small, blunt, relatively harmless cubes, whereas laminated glass holds the broken shards together via a polymer (PVB) interlayer.

Can toughened safety glass be resized at the site?

No, any cutting or drilling must be done before the toughening process, otherwise the glass will shatter immediately.

What is the fracture test?

A test for toughened glass to ensure it breaks safely into a minimum number of small particles (typically at least 40 in a 50x50 mm square) rather than large, dangerous shards.

How is laminated glass tested for delamination resistance?

It is subjected to a Boil Test (immersed in boiling water for 2 hours) to check for bubbles, delamination, or cloudiness.

IS 2553 Part 1

: 1990

Safety Glass - Part 1: General

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This standard specifies the requirements and testing methods for general purpose safety glass (toughened and laminated) used in architectural, building, and structural applications. It sets benchmarks for dimensional tolerances, impact resistance, fragmentation safety, and optical clarity.

Lays down general requirements for safety glass used in buildings.

Quick Reference Values

light transmission clear glassNot less than 70%

fracture test minimum particles 4to12mm40 particles in 50mm x 50mm area

boil test duration laminated glass2 hours

shock test steel ball mass227 g ± 2 g

shock test drop heightVaries by thickness (e.g., 2000 mm to 3000 mm)

Practical Notes

Toughened glass cannot be cut, drilled, or edge-worked after the toughening process; all fabrication must be completed prior to heat treatment.

Laminated safety glass is highly recommended for overhead glazing (like skylights) because the interlayer retains shattered glass pieces, preventing them from falling.

For visual distortion checks, glass should be viewed in transmission at the intended installation angle rather than purely horizontally or vertically.