Abstract
A numerical grading system has been established for white gold alloys using the ASTM Yellowness Index D1925, an existing colour quality standard. The Index is calculated from the CIE (International Commission of Illumination) Tri-stimulus values, X, Y and Z, and the scale is linear, so that as the number decreases, the alloy becomes whiter.
This Index provides values that have good correlation with visual assessments and permits easy differentiation of colour without knowledge of an alloys composition. The use of a spectrophotometer instrument provided a quick means of sample colour measurement, with high precision and accuracy.
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Steven Henderson is the Metallurgical Manager at Cookson Precious Metals Ltd. After obtaining his Honours degree in Material Science from Coventry University, he joined the Sintered Products division of Turner and Newall Ltd, which was part of their automotive supply chain. There he worked on a number of new alloy and process development projects for various leading automotive suppliers. Since joining Cookson Precious Metals Ltd, he has worked on a number of development projects for new alloys and new manufacturing processes, including development of their powder metallurgy projects.
Dippal Manchanda is the Chief Assayer at the Birmingham Assay Office, working on both non-statutory technical projects and day-to-day assay management. He holds a Masters degree (MSc) in inorganic chemistry and has over 20 years experience in assaying and the examination of precious metals and alloys. He is also a Member of the Royal Society of Chemistry, a Chartered Chemist and Chartered Scientist. Since completing his Masters Degree, Dippal has spent his entire career in the field of precious metals and has been involved in several projects including setting up a state of the art Gold/Silver Medallion Manufacturing facility for a Public Sector Undertaking in India. In his role as Chief Assayer, he is responsible for setting, managing and maintaining high analytical standards throughout the Assay Office and providing scientific and technical support on a day-to-day basis to both statutory and non-statutory part of business.
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Open Access This is an open access article distributed under the terms of the Creative Commons Attribution Noncommercial License ( https://creativecommons.org/licenses/by-nc/2.0 ), which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.
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Henderson, S., Manchanda, D. White gold alloys:. Gold Bull 38, 55–67 (2005). https://doi.org/10.1007/BF03215234
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DOI: https://doi.org/10.1007/BF03215234