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<p>[QUOTE=&quot;Sallent, post: 2839887, member: 76194&quot;]There is a scientific study that sought to analyze the exact surface and interior composition of different Roman coins, and prepared blanks and used the different suggested techniques for how the Romans might have enriched the surface of coins to make debased coins look like good silver, to see which techniques could replicate the actual surface and interior structures of Roman coins.</p><p><br /></p><p>The study was titled <b>&quot;Silver surface enrichment of silver-copper alloys: a limitation of for the analysis of ancient silver coins by surface tehcniques,&quot;</b> which was published in the <b>Nuclear Instruments and Methods in Physical Research B226 (2004) 153-162. </b></p><p><b><br /></b></p><p>Their research shows that they could replicate the differing concentration of silver surface and internal layers of Roman coins using several theorized pre-production methods, and that post-production treatment of the flans was not necessary.</p><p><br /></p><p>The team examined the methods of enrichment proposed by L.H. Cope in the article <b>&quot;Methods of Chemical and Metallurgical Investigation of Ancient Coinage</b>,&quot; <b>RNS Special Publication No. 8, 1972, p.261.</b> Cope proposed 5 steps, (1) casting a button of silver-copper alloy, (2) heating the button in air to form a layer of copper oxides, (3) acid-pickling the blank for removing the copper oxides and revealing the silver-phase, (4) hammering the blank for spreading silver-phase laterally, and (5) striking the blank.</p><p><br /></p><p>The results demonstrated that for coins of more than 15%-20% Ag in the silver-copper alloy, steps #2 and #4 were not necessary as the heating achieved during the casting of the original silver-copper alloy button was sufficient to create a substantial silver rich surface. However, for coins of lower Ag content, steps #2 and #4 were still valid.</p><p><br /></p><p>So basically, the Gordian and Volusian coinage would have been enriched by heating flans of silver-copper alloy, acid-pickling the flans, and subsequently striking the flans with the dies. That was all there was to it.</p><p><br /></p><p>As for the pickling mixture, I&#039;ve read somewhere else, though I can&#039;t recall the source, that urine might have been used as it was an acid that was in ready supply to the Romans. As you all know, urine is mildly acidic. So yeah, there is a possibility that precious coin you are holding was soaking in a tub of Roman urine 1,800 years ago.</p><p><br /></p><p>Now, obviously once you get to really low silver content like 5%, no amount of heating, pickling, striking, etc, will make that puppy look like silver, so plating would have been used. How the Romans plated those coins, I&#039;ve yet to examine. Maybe someone here has insight into that.[/QUOTE]</p><p><br /></p>

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