Trial needle
A test needle , also known as a pen needle, is a stick made from a precious metal alloy that is used for the test . There are trial needles with different degrees of precious metal fineness.
Basics
Precious metals like gold and silver are made in different alloys . Gold is often alloyed with copper or silver or both metals. In order to be able to precisely determine the composition of an alloy, different trial needles are required. 24 trial needles in different caratings are used for gold . The needles contain gold, silver and copper in different mixtures and thus enable the investigation of gold alloys. Often the different trial needles were made by the testers themselves using a table. Agricola describes in his book "Twelve Books of Mining and Metallurgy" trial needle sets that contain different proportions of gold and silver. The first needle contains one part gold and 23 parts silver, the 24th needle contains pure gold. These needles can be used to test gold and silver alloys. For gold-copper alloys, Agricola describes another needle set with 13 needles. He describes three other needle sets for silver-copper alloys, they consist of 28, 24 or 31 needles. For alloys that consist of all three metals, Agricola describes a needle set with 13 trial needles and another consisting of 37 needles. In addition to these needles, Agricola offers another needle set for gold-silver-copper alloys, which consists of 28 needles. Each needle in the individual sets has a different proportion of gold, silver or copper; some needles are made of pure metal, others are made of only two metals. This high number of needles made it possible to check all common precious metal alloys, especially coins, of the time.
Today's application
Trial needles are still used today to check precious metals by means of the sample and are made in different alloys of gold, silver and copper. As a rule, the alloys used here are those that are most common for precious metal objects. Instead of a trial needle made from one piece, trial needles made of a copper, brass or bronze pin are also used, to which a pin or a lamella with the appropriate alloy is soldered. In addition to the trial needles, there are also trial asterisks. The number of test needles or test asterisks used depends on the demands placed on the accuracy of the sample. There are different needles with the same gold content, but in different colors, especially for checking different gold alloys. The expert calls the composition of trial needles of the same fineness but different colors a trial game. A sample needle assortment for the most frequently used fineness consists of twelve sample needles. Of these, three trial needles are suitable for silver tests , three trial needles for yellow gold tests , three trial needles for red gold tests and three trial needles for white gold tests . The fineness for silver is graded in 0.800, 0.835 and 0.925. For gold, the needles are graded in 0.375, 0.585 and 0.750.
literature
- Karl Hradecky: The sample of precious metals . Springer Verlag Wien GmbH, Vienna 1930
Individual evidence
- ↑ Bruno Kerl: Metallurgical trial art for use in lectures and for self-study. Published by Arthur Felix, Leipzig 1866.
- ↑ Johann Christoph Adelung: Grammatical-critical dictionary of the High German dialect. Third part, printed by Anton Pichler, Vienna 1808.
- ↑ The well-experienced Scheid artist, or practical instruction on how to try and separate all ore and metals, especially gold and silver, with little expense and effort but with great benefit. Frankfurt and Leipzig 1755.
- ^ Georg Agricola: Twelve books on mining and metallurgy. In commission VDI-Verlag GmbH, Berlin.
- ^ Federal Law Gazette for the Republic of Austria. Year 2001, 136th Ordinance: Hallmarking Ordinance ( Memento of May 12, 2013 in the Internet Archive ) (PDF; 26 kB) (last accessed on March 1, 2013).
- ↑ Walo Wälchli and Pierre Vuilleumier: Die Edelmetall-Strichprobe (last accessed on March 1, 2013).