Plating thickness is usually measured with X-ray fluorescence (XRF), which reads the layer without damaging the piece. When a dispute needs a definitive answer, a lab cuts a sample and measures the layer under a microscope, a method called cross-section microscopy.
Both methods give a figure in microns that you can compare with your order. Without a measurement, a thickness claim is only a promise.
XRF testing
An XRF instrument fires X-rays at a small spot on the piece and reads the energy that comes back. From this it calculates the thickness of the plated layers and identifies the metals in them. The test takes seconds and leaves no mark. The international standard for this method is ISO 3497.
XRF works best on flat, clean areas. Readings on curved, textured or stone-set surfaces are less reliable, and the instrument must be calibrated for the right layer system, such as gold over nickel over brass. Ask which spot was measured and take readings on several pieces, not one.
Cross-section microscopy
The lab cuts through the piece, mounts and polishes the cut face, and measures each layer under a microscope. The method is described in ISO 1463. It shows the gold, any barrier layer and the base metal directly, and reveals problems such as porosity or uneven coverage.
Because it destroys the sample and takes longer, it is used to settle disputes, validate a new supplier or calibrate XRF readings, not for every lot.
Other methods
- Coulometric testing dissolves a small spot of the plating and calculates thickness from the electric charge used. It is accurate for some layer systems and is covered by ISO 2177.
- Weight gain compares a piece before and after plating. It gives an average, not the thickness at any point.
- Acid or touchstone tests show whether gold is present, not how thick the layer is.
Setting a sensible testing plan
- Agree the target thickness and a minimum per measuring spot in the order.
- Test the approved sample so you have a reference figure.
- Test a few pieces from each bulk lot by XRF at a lab or at pre-shipment.
- Use cross-section only when XRF results are disputed or the supplier is new.
What this means for a buyer
A thickness figure on the order plus a test on the bulk lot protects you from quiet downgrades between the sample and the shipment. See how to make sure the order matches the approved sample.
Creston & Co works for buyers only, for a fixed fee agreed in writing. We draw samples from the bulk lot in Rajkot, send them to NABL-accredited labs and supervise packing. Start with a free sourcing review.