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Example: A tungsten-copper piece (alloy 80/20) was used for a test series to illustrate the
penetration depth of the magnetic measurement. This paramagnetic material is often used for
the forgery of coins. The MagneticScreenScale showed a value of -0.063 g for the pure disc. In
order to simulate a tungsten-copper inclusion in gold, diamagnetic brass discs were placed in
layers under the tungsten-copper piece. Up to 5 discs (2.0 mm in total) continued to result in
negative values. From the sixth disc (2.4 mm in total), the value became slightly positive (0.010
g) and the MagneticScreenScale thus lost its unmasking effect, as the distance between the
tungsten-copper piece and the magnet became too large.
Pure materials:
The following table provides an overview of the different magnetic properties of pure metals
and the values obtained with the MagneticScreenScale.
Diamagnet
Positive
Value (+)
Bismuth
Beryllium
Antimony
α-Tin
Tellurium
Silver
Zinc
Gold
Lead
Copper
The figure on the following page provides an overview of the magnetic properties of pure metals
and their respective strength. The strength is measured in the so-called magnetic susceptibility
-9
3
and given in 10
m
Silver, platinum and palladium can also be tested for foreign metal inclusions with the
MagneticScreenScale. However, please note that the counterfeit material must have opposite
magnetic properties to the corresponding precious metal so that it can be detected by the
magnetic scale. Palladium in particular exhibits strong paramagnetic properties. For example, a
bismuth core in palladium can be detected, while a titanium core is not detected, as titanium
also has pronounced paramagnetic properties. In the example mentioned, however, the weight
and/or dimensions would deviate greatly from the original, as titanium has a significantly lower
density than palladium (4.50 g/cm
/kg (reverse sign!).
3
vs. 11.99 g/cm
Paramagnet
Negative
Value (-)
β-Tin
Osmium
Iridium
Tungsten
Ruthenium
Magnesium
Aluminium
Tantalum
Molybdenum
Platinum
Rhodium
Titanium
Chromium
Palladium
3
).
Ferromagnet
Strongly negative
Value (-)
Iron
Nickel
Cobalt
29
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