Measuring Tarnish Resistance
Tarnish resistance is measured through a scientific process using the CIELAB standard colour measurement system. A colorimeter is used to measure the change in surface colour on each test sample after exposure to the tarnish tests. The ‘dark to light’ scale (the central vertical axis in the double-cone colour diagram) is the critical measure used to gauge the degree of tarnish film that is formed on the silver alloy test samples.
Argentium alloys are required to pass predefined levels on the ‘dark to light’ scale, using the CIELAB system. The results from all three tests are combined, using the following weighting coefficients, to give a Tarnishing Index value:
- Sulphur - 0.6
- Perspiration - 0.2
- UV - 0.2
The overall test results are shown in Fig 1. AQL - the Argentium Qualification Line - is the minimum tarnish resistance requirement for Argentium silver alloys.
Read more about this topic: Argentium Sterling Silver
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