BS 7031:1988 pdf free download.Colours of gold alloys.
0 Introduction
In the manufacture and sale of articles made of or coated with gold alloy0 the colour of the surface of the product Is an Important characteristic. However, at present, an undue variety of colours of surface finishes is offered to the public. Some of these colours differ only slightly from one another.
The range of colours defined in BS 7031 is Intended to enable the manufacturer to limit the stock of different colours that he might be obliged to keep. It will also enable the purchaser to define his requirements with precision by referring to the designations given within BS 7031 end so avoid the need for purchasing orders to be accompanied by colour samples.
1 Scope and field of application
BS 7031 specifies a limited number of colours of gold alloys.
By specifying a range of gold alloy colours, BS 7031 enables a corresponding range of polished gold colour slips to be produced for comparison purposes for use in routine transactions between manufacturer and purchaser. It applies to jewdiery, and to watch cases and accessories made of gold alloys or watch cases and accessories with gold alloy coverings.
2 References
CIE Publication No. 15, Colorimetiy.
CIE Publication No. 38, Radiometric and photometric charac(er/st/cs of materials and their measurement.
3 DefinitIon
colour of gold alloy: A three-dimensional colour space represented by the chromaticity co-ordinates x and y and reflectance p, In accordance with CIE Publication No. 15.
NOTE — When necessary for special purposes or In the field of national standardization, the chromaticity co-ordinates may be converted to other Internationally or nationally agreed systems (e.g. CIE 1976 Lab colour space or CIE 1976 Luv colour space).
4 Range of colours and designation
The range of colours according to chromaticity co-ordinates are given in table 1.
5 Measurement method
5.1 Preparation ‘of the samples
The samples to be measured shall have a polished surface. The finishing shall be continued untfl a constant reflectance grade has been achieved.
5.2 Apparatus
5.2.1 Integrating sphere spectrophotometer.
5.2.2 Standard Illuminant, comprising a light source yielding the spectral distribution similar to that of the standard light source D 65 (daylight) specified In CIE Publication No. 15.
5.3 Test procedure
Measure the spectral reflectance In accordance with CIE Publication No. 38.
6 Colour slips
For comparison purposes in routine transactions, it Is recommended that a range of polished gold alloy colour slips should be used that are prepared so that the colour of the surface of each colour slip accords with the chromaticity co-ordinates given in table 1 when measured in accordance with clause 5.
See the annex for the recommended chemical composition of colour slips.