-- 作者： 有誰賣甲蟲 -- 發表時間： 2020/03/04 08:52:23pm [這篇文章最後由有誰賣甲蟲在 2020/03/04 08:53:28pm 第 1 次編輯] Every material has a set of physical and chemical properties associated with it. Any material identification will be based on one or more of these properties. This article covered the easiest to make use of. However, every property adds confidence to the identity of the material especially if someone is trying to duplicate any one property. Duplicating multiple properties is non-linearly more difficult than duplicating just one. Some material properties not covered in the above article include, but are not limited to: electrical properties (there are many, don’t limit yourself to resistance), hardness, tensile strength, compression set, thermal expansion rate… the list is massive. For those that really want to be sure without paying for a gas chromatograph and/or mass spectrometer, measure several properties at a given temperature (and pressure) then measure the same properties at multiple temperatures – ideally a large temperature range. The more properties tested the more confidence you can have in the identity of the material; the more conditions under which the properties are tested (i.e. temperature) additional confidence may be achieved. Keep in mind that to reproduce just the density and acoustic properties would be very difficult. Reproducing them at multiple temperatures would be even more difficult. At this point, the forger would need to be operating on a massive scale to be profitable, they would need a lot of skill and equipment and in the case of coins they would have the attention of the secret service (for US coins) as soon as one was identified. For silver bars not issued by any government, they would have the FBI and/or any relevant international agencies to worry about. So again, anyone that could produce such a perfect forgery would never be a forger to begin with; they would make a generous salary working in a wide range of legal capacities. The largest precious metal fraud I know of was the incident were tungsten bars were plated in gold and introduced to national gold stockpiles. The tests outlined on this page would have identified those fake bars, its (temporary) success depended on getting the fake bars into the trusted stockpile and thus avoid having to pass all but the most cursory tests. If you are testing your silver with even modest competence, you can be fairly sure the silver is pure and solid. For coin collectors this is all but useless since it only applies to identifying the material the object is made of, not who made the object or when. -- 作者： 小多仔 -- 發表時間： 2020/03/04 10:10:50pm 喔＿