Overview
ISO 24117:2020 - "Tableware, giftware, jewellery and luminaries, made of glass - Glass clarity - Classification and test method" defines a harmonized system for classifying glass clarity of non‑coloured mineral glass used in tableware, giftware, jewellery and luminaries. The standard specifies objective measurement methods (spectrophotometry and chemical analysis) and clear pass/fail criteria for the designations “clear glass” and “ultra‑clear glass” to support consistent quality, labeling and procurement.
Key topics and technical requirements
- Scope: Applies to non‑coloured mineral glass parts that can be sampled; excludes building glass, watches, containers, medical and laboratory glass, and other technical uses.
- Classification criteria: Based on three measurable properties:
- Lightness (L*) and chroma (C*) (colourimetric values calculated from internal transmission).
- Iron oxide content (Fe2O3) expressed in mg/kg, since iron strongly affects transparency and color.
- Thresholds:
- Ultra‑clear glass: L* ≥ 98.8, C* ≤ 0.5, Fe2O3 ≤ 140 mg/kg.
- Clear glass: L* ≥ 98.0, C* ≤ 0.5, Fe2O3 ≤ 200 mg/kg.
- Test methods:
- Spectrophotometric total transmittance measured per CIE 15 (Colorimetry) using a double‑beam UV‑Vis spectrophotometer (integrating sphere preferred).
- Measurements taken on two sample thicknesses (10 mm and 30 mm) to compute internal transmission for an intermediate thickness (20 mm) - reducing refractive‑index dependence.
- Iron content determination via suitable analytical technique (e.g., wavelength‑dispersive XRF as referenced).
- Sampling and sample prep: Detailed procedures for cutting, grinding and polishing parallel faces to tight tolerances (thickness ±0.05 mm) and special guidance when parts are coated (melting/recasting of ~200 g may be required).
Applications and users
- Manufacturers of tableware, giftware, jewellery and luminaries who need to certify product clarity or market “clear” / “ultra‑clear” glass.
- Quality control and testing laboratories implementing reproducible spectrophotometric and chemical tests.
- Procurement, product designers and retailers specifying clarity requirements in contracts and product sheets.
- Regulatory and standards bodies aligning consumer quality expectations internationally.
ISO 24117 supports consistent product labeling, helps prevent misleading marketing claims, and enables objective acceptance criteria in quality agreements.
Related standards
- CIE 15 - Colorimetry (normative reference for colourimetric measurement).
- Note: Lead crystal categories follow EU Council Directive 69/493/EEC and are excluded from ISO 24117’s scope.