Assay examination of cultural values and antiques

Assay examination of cultural property - the study of the metal from which the decoration is made. Does the assay mark, the nameplate, whether they are real, whether the assay mark corresponds to the true alloy composition of the product, all these questions must be answered by the assay examination.

The modern interstate GOST 30649-99 regulates the compositions of precious alloys (grades), which are used for the manufacture of jewelry, the composition of which has been worked out for years and, moreover, it is harmonized with the ISO MS ISO "Jewelry. Samples of noble metals in alloys". This document contains requirements for the chemical composition of 40 alloys, which include: 26 grades 2-5 - you are component alloys based on gold from 958 to 375 standard; 5 grades of alloys based on silver from 960 to 800 tests; 6 alloys based on platinum from 950 to 900 standard; 3 grades based on palladium-850-500, as well as pure gold grades for jewelry work. These alloys have a very wide range of consumer properties - high corrosion resistance, sufficient ductility, optimal casting properties, abrasion resistance, a range of colors of alloys, etc. But along with standard alloys, jewelers also use alloys for the manufacture of products that are not regulated by any regulatory document , providing a guarantee only for the sample. However, to assess the corrosion resistance of alloys, it is important not only the sample, but also the atomic content of precious metals (the number of atoms of the base metal in 100 alloy atoms). Analysis of the most common gold alloys made it possible to establish and compare the atomic content of gold in jewelry alloys. Note that gold can be alloyed with a sufficiently large amount of silver or base metal without seriously impairing the corrosion resistance at room temperature. At room temperature and 50% (at.) Gold content in the alloy, the addition of copper and silver does not reduce the corrosion resistance to aggressive environments

Therefore, the question of "sample" and "quality" of products should be the same and investigated during the identification examination and examination of the authenticity of products.

Under the conditions of Assay Supervision , the sample of precious metal is usually established by the Wolfgard method, on the assay stone, by the assay melting method. However, the question of determining impurities in an alloy in combination with a breakdown is solved only with the help of X-ray fluorescence spectroscopy. So, the composition of the metal, which is studied using spectral methods, in particular X-ray fluorescence analysis, makes it possible not only to determine the authenticity of the alloy, but also to establish its correspondence to the content of negative, toxic impurities.

In the world jewelry market, there are a large number of trade names for precious and non-ferrous alloys used by manufacturers, restorers and collectors of jewelry, in particular, some of them do not contain the precious metal at all, but resemble it in appearance. Domestic industry standards provide for the high-quality content of the precious alloy, provides an opportunity to regulate the physical and mechanical properties in a targeted manner, ensure the ability of the alloy to pour into appropriate shapes and form due to pressure without the appearance of defects. The question of determining impurities of a precious metal, their quantitative content, which are not standardized by standards, should be considered not only from the standpoint of their harmful effect on the human body, but also from the standpoint of preserving the appearance, beauty of color, and corrosion resistance in general. However, this topic is just beginning to acquire relevance today.

Quantitative falsification of jewelry arises as a result of consumer deception due to a significant deviation in the parameters of the jewelry (weight, volume, length). The use of inaccurate measuring instruments, as well as the inability to use measuring instruments, is the most common method of quantitative falsification. In this case, counterfeit measures and instruments (scales) are used without a verification mark and certificate. That is, the professional qualifications of a jewelry expert should include metrological competence.

Weighing of the jewelry takes place on an analytical balance (or the weight is set according to the accompanying documents for the product). Gold, palladium, platinum products - with an accuracy of 0.001 g, silver - up to 0.1 g. Small products are solved with an accuracy of 0.01 g, large ones - up to 0.1 g. Counterfeiting leads to deception of consumers by selling products at higher prices.