Overview
ISO 8654:2018 - Jewellery - Colours of gold alloys - Definition, range of colours and designation - defines a limited set of standardized gold alloy colours and the methods to measure and designate them. It applies to objects made of, or coated with, gold alloys and enables clear, repeatable colour specification between buyers, manufacturers and testing laboratories without exchanging physical colour samples.
Key topics and technical requirements
- Colour designations: Seven standard colour classes (0N–6N), ranging from yellow‑green (0N) through pale/ light/ yellow, pink, red to dark red (6N).
- Measurement methods:
- Quantitative - spectral reflectance measured by an integrating‑sphere spectrophotometer (reference geometry di:8° or 8°:di) with specular component included (SCI), D65 standard illuminant and 2° standard observer.
- Qualitative - visual comparison against polished colour slips (Annex A).
- Sample preparation: Flat, defect‑free, mirror‑polished surface; metallographic final polish (broadcloth with 1 µm abrasive); clean with microfiber + isopropyl alcohol; measure within 120 minutes of polishing.
- Measurement practice & reporting: Average of 5 measurements with repositioning and rotation between reads. Results reported in xyY (x,y to 4 significant digits; Y to 1) and convertible to CIE 1976 Lab* and LCh (a*, b*, C*, h with 2 significant digits; L* with 1).
- Nominal values and tolerances: The standard provides numerical nominal coordinates and tolerances for xyY, Lab* and LCh colour spaces and graphical tolerance figures.
- Annex A: Suggested alloy compositions for preparing colour slips (e.g., approximate Au/Ag/Cu mixes such as 585/300–340 for 0N and 750‑based alloys for others) - noted as indicative only, since surface finish and metallurgy also affect perceived colour.
Applications and users
ISO 8654:2018 is used by:
- Jewellery manufacturers and designers for precise colour specification.
- Quality control and metrology labs performing colour verification and acceptance testing.
- Suppliers and retailers to standardize product listings and avoid disputes over colour.
- Assay offices and certification bodies for conformity assessment related to appearance.
- Buyers and procurement teams to define requirements in contracts and purchase orders.
Practical benefits include consistent colour communication, improved quality control, fewer sample exchanges, and defensible acceptance criteria based on standardized tolerances.
Related standards
- CIE Publication No. 15 - Colorimetry (normative reference for measurement methods).
- CIE Publication No. 38 - radiometric/photometric characteristics (useful background).
Keywords: ISO 8654:2018, gold alloy colours, jewellery standard, colour measurement, spectrophotometer, xyY, Lab*, colour designation, colour slips, integrating sphere.
