ISO 16293-2:2017

Overview

ISO 16293-2:2017 - Glass in building - Basic soda lime silicate glass products - Part 2: Float glass - specifies dimensional and minimum quality requirements for float glass used in building applications. The standard applies to float glass supplied in stock sizes (jumbo, split, supplied sizes) and final cut sizes, and covers measurement methods, tolerances and acceptance criteria for optical and visual faults.

Keywords: ISO 16293-2:2017, float glass, glass in building, soda lime silicate glass, glass tolerances, optical faults, visual faults, glazing standards.

Key topics and technical requirements

• Scope and definitions

  • Applies to basic soda‑lime silicate float glass for building use; terms defined in ISO 16293‑1.
  • Stock sizes include jumbo (nominal lengths 4 500–6 000 mm; width usually 3 210 mm), split and supplied sizes; final cut sizes have minimum dimensions (≥100 mm sides, ≥0.05 m² area).

• Dimensional requirements

  • Thickness: Measured as the average of four micrometre readings (one at each side) to 0.01 mm. Specific tolerances are given by nominal thickness (e.g., 2 mm ±0.2 mm; 3–6 mm ±0.3 mm; 8–12 mm ±0.6–0.8 mm; up to 25 mm ±1.2 mm).
  • Length, width and squareness: Tolerances for jumbo/split and supplied/final cut sizes are defined (typically ±2–5 mm depending on size). Squareness limits are given by allowable diagonal differences.

• Quality requirements - optical and visual faults

  • Optical faults (distortion): Assessed using a zebra test (black/white stripes: 25 mm stripes, screen distance and lighting specified). Test setup: glass 4.5 m from screen; observer at 9 m; illuminance 400–1 200 lux; dark non‑reflective surroundings. Acceptance is based on critical viewing angle α (e.g., 1.9–2.7 mm glass: α ≈ 40°; 3 mm: 45°/40°; ≥4 mm: 50°/45° in specified zones).
  • Visual faults: Includes spot faults (nucleus + halo categories) and linear/extended faults (deposits, scratches). Spot categories are defined by nucleus and halo size ranges (examples: nucleus ≤1.0 mm with halo ≤3.0 mm; larger classes up to halo >9.0 mm).
  • Edge defects: Entrant, emergent faults and bevels are illustrated and specified for final cut sizes; dimensions (h1, h2, p, d, e) are measured.

• Measurement methods

  • Thickness by caliper micrometre; halo measurement method detailed in Annex A; optical distortion by rotation/zebra-screen method; visual inspection against matt black backgrounds.

Applications and who uses it

• Manufacturers and mill operators - set production and stock-size tolerances for float glass.
• Glass processors and fabricators - verify supplied stock and final cut sizes before toughening, insulating unit assembly or tempering.
• Architects, façade engineers and specifiers - reference for procurement specs and performance criteria for glazing.
• Quality control, inspectors and procurement teams - acceptance criteria for deliveries, inspection protocols and dispute resolution.

Related standards

• ISO 16293-1 (terminology and scope for basic soda‑lime silicate glass products)
• Other ISO/TC 160 publications on glass in building (see ISO website for the series).

Using ISO 16293-2:2017 helps ensure consistent dimensional quality and predictable optical/visual performance of float glass in building façades, windows and other architectural glazing applications.