The Top 10 Methods of testing Silver
A touchstone was for centuries a popular method of testing silver purity. It was often made from a wedge of thick slate upon which the silver item was rubbed. The colour of the resulting stripe was compared to the results from known metals. If the colour was similar, then further testing could be undertaken by applying "Aqua Regia" which was a solution of Nitric and Hydrochloric acids. Assay officers, mine officials and mineralogists use to carry their touchstone on the end of a fob chain - hence the pendant bale frequently found at the top of the touchstone.
Silver is not magnetic, therefore if the metal you are testing is magnetic then it is not silver. If it is not magnetic this only proves it might be silver or silver-plated.
Silver has a distinctive ringing sound when dropped onto a hard surface or struck with a small hammer. Specialist equipment is sometimes used to analyise the specific harmonics however if you make a clean strike of the metal and there is no ringing sound then this is the first alarm that what you have may not be silver.
The test which is frequently used by ourselves and other jewellers is to apply a swab of "Schwerter's" solution, which contains nitric acid and potassium dichromate, either directly to the silver or to a fine sample extracted from the piece by filing or drilling. We always ensure that it is applied to a very small area of the piece that it is not clearly visible, such as the underside of the piece because it leaves a greyish residue on the surface. When applied to testing paper the solution will turn a deep red if the metal is 90 to 99% pure silver. The test is quick and easy although its problem is that its not as accurate as other methods simply as it is often too difficult to determine the purity of the acids used. Moreover Nitric Acid is an extremely hazardous substance requiring specialist care.
Hardness and malleability
Silver is relatively soft and malleable. If the item permits, bending it easily is sign of real silver. Also if you try and file a harder metal then the filing will be difficult compared to silver.
These are stamped on the item and give a legal assurance or warranty for the degrees of purity for different types of silver. in the case of sterling silver for example that percentage is 92.5%. The British Hallmarking Council provides a legal and technical explanation for the hallmarking of silver.
Mass spectrometry is a technique for analyzing the molecular structure of a chemical structure. For precious metals ICP-MS (Inductively-coupled plasma mass spectrometry) is used to detect and separate the ions of the metal and because of its accuracy, such instruments frequently used by assay offices.
Another method used by the assay office is the melting of a sample taken from the metal which is then chemically assayed.
This device is a handheld Niton x-ray fluorescence analyzer. It uses miniaturized x-ray tubes in a thermoelectrically cooled detector with an onboard data controller that analyses its results that are displayed on its screen. A quick and fairly accurate method of testing the purity of any metal although it does not have very deeppenetration and therefore can be foxed by a heavy silver plate.
The specific gravity for silver is 10.49 and its measurement can be taken by using various water displacement techniques.