In our previous post on non-destructive assays, we covered spectrophotometry – which analyzes the color of an object by simply measuring the light it reflects. Unfortunately, spectrophotometry only works on an object’s outermost layer and usually provides varied results depending on what is being tested. Today, we’ll go over other non-destructive assays that provide more reliable results.
This assay uses ultrasound to measure changes in the consistency of the material being tested. To conduct the test, an ultrasonic flaw detector (pictured) generates an ultrasonic pulse and emits it via a stethoscope-like transducer that is pressed against the test subject. Ultrasonic waves travel through any medium in the same direction until they meet a different material, which causes them to reflect back to their source. The transducer detects any changes in the ultrasonic pulse to find out if the outside and inside of an object are made of the same material.
Ultrasound assays are a service we offer here at MGS. It’s the ideal test for quickly catching counterfeit bullion (e.g. tungsten-plated bars) or sorting out precious metal plated items from solid ones.
Thermal conductivity testing
As the name suggests, this test measures how well a material conducts thermal energy. A specialized heat-generating sensor is attached to the object. The heat from the sensor dissipates into the object. The sensor records the temperature and time elapsed to calculate the thermal transport properties of the material. Since every metal has unique thermal conductivity properties, you can use the test results to narrow down exactly which metal makes up the object.
Even though thermal conductivity testing is extremely accurate, keep in mind that the results only apply areas where the heat reached. You’ll want to test in multiple spots to check if the amount of precious metals are consistent throughout a piece.