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<p>[QUOTE="Sulla80, post: 3954019, member: 99456"]While I will claim interest, it is as a collector, and non-expert that I share the following. Other references, additions, corrections always appreciated.</p><p><br /></p><p><b>Timing:</b> Here's a graph of the table in <a href="https://smile.amazon.com/gp/offer-listing/0801852919/ref=tmm_hrd_used_olp_sr?ie=UTF8&condition=used" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://smile.amazon.com/gp/offer-listing/0801852919/ref=tmm_hrd_used_olp_sr?ie=UTF8&condition=used" rel="nofollow">Harl</a> (Ch. 6 - The Great Debasement and Reform A.D. 193-305 Table 6.2 p 130)</p><p>[ATTACH=full]1041594[/ATTACH]</p><p>And another graph from <a href="https://www.jstor.org/stable/10.2307/42663317" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://www.jstor.org/stable/10.2307/42663317" rel="nofollow">G. C. Haines 1941</a> illustrating data from <a href="http://numismatics.org/zfn/38060000322628/125297.pdf" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://numismatics.org/zfn/38060000322628/125297.pdf" rel="nofollow">J. Hammer </a>(1908) the decline in silver content over time - more recent studies and techniques for analyzing the silver content may have improved on this view.</p><p>[ATTACH=full]1041588[/ATTACH]</p><p>Here is a <a href="http://money.visualcapitalist.com/deaths-roman-emperors-vs-silver-coin-content/" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://money.visualcapitalist.com/deaths-roman-emperors-vs-silver-coin-content/" rel="nofollow">prettier graph</a> with a less clear source of data.</p><p><br /></p><p><b>Process:</b> There were multiple processes potentially used to make plated counterfeit and official coins throughout time. While there are several candidates for silver plating in ancient Rome, there is uncertainty about the process used for late Roman coins. Here are several candidates (there are others mentioned in the references below):</p><ul> <li><b>"diffusion bonding" or "Sheffield plating" </b>: silver copper sheets heated together reported in use for Roman Republican fourrée denarii, wrap copper flan in a silver foil and heat. This is considered too labor intensive to have been used at scale in late roman empire</li> <li><b>"dipping in silver chloride" </b>- Blanks were maintained hot, dipped in molten silver chlorides, and quenched in a bath <br /> </li> <li><b><b>"mercury silvering", "amalgam plating", or "fire gilding"</b> -</b> a good way to get mercury poisoning - dissolve silver in mercury, then spread on the flan like peanut butter, then evaporate the mercury with heat, this technique is mentioned as a possibility for late roman coins.</li> <li><b>"depletion silvering", "pickling" or "blanching" </b>- take a copper-silver alloy - use citric acid or vinegar to leach out the copper and enrich silver content of the outer surface, then strike to produce a silver surface plating which seems to be a leading hypothesis for later Roman coins.</li> </ul><p>Selected references for further reading:</p><ul> <li><font size="4"><a href="https://www.worldcat.org/title/coinage-in-the-roman-economy-300-bc-to-ad-700/oclc/33817980" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://www.worldcat.org/title/coinage-in-the-roman-economy-300-bc-to-ad-700/oclc/33817980" rel="nofollow">Harl, K. W.</a> (1996). <i>Coinage in the Roman economy, 300 B.C. to A.D. 700</i>. Baltimore: Johns Hopkins University Press</font></li> <li><font size="4"><a href="http://www.jstor.org/stable/42663317" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.jstor.org/stable/42663317" rel="nofollow">Haines, G. C.</a> (1941). THE DECLINE AND FALL OF THE MONETARY SYSTEM OF AUGUSTUS. <i>The Numismatic Chronicle and Journal of the Royal Numismatic Society,</i> <i>1</i>(1/2), 17-47</font></li> <li><font size="4"><a href="https://doi.org/10.1017/S0003581500070335" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://doi.org/10.1017/S0003581500070335" rel="nofollow">Susan La Niece</a> (1990) Silver Plating on Copper, Bronze and Brass. <i>The Antiquaries Journal,</i> <i>70</i>(1), 102-114. doi:10.1017/S0003581500070335</font></li> <li><font size="4"><a href="http://researchonline.ljmu.ac.uk/id/eprint/5590/1/373706.pdf" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://researchonline.ljmu.ac.uk/id/eprint/5590/1/373706.pdf" rel="nofollow">Cope, L. H.</a> , (1974) “The metallurgical development of the Roman Imperial coinage during the first five centuries A.D.”, PhD Thesis, Liverpool Polytechnic, Liverpool John Moores University. doi:10.24377/LJMU.t.00005590</font></li> <li><font size="4"><a href="https://www.forumancientcoins.com/historia/Silvering%20on%20Roman%20coins.pdf" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://www.forumancientcoins.com/historia/Silvering%20on%20Roman%20coins.pdf" rel="nofollow">C. Vlachou, J.G. McDonnell, R.C. Janaway</a> (2002) Experimental investigation of silvering in late Roman coinage, Mat. Res. Soc. Symp. Proc. Vol. 712</font></li> <li><font size="4">Pliny describes a technique for plating in <a href="http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.02.0137:book=34:chapter=48&highlight=plating" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.02.0137:book=34:chapter=48&highlight=plating" rel="nofollow">Naturalis Historia book 34 ch. 48.</a></font></li> <li><font size="4"><a href="http://www.jstor.org/stable/43580265" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.jstor.org/stable/43580265" rel="nofollow">Keyser, P. </a>(1995). GRECO-ROMAN ALCHEMY AND COINS OF IMITATION SILVER. <i>American Journal of Numismatics (1989-),</i> <i>7/8</i>, 209-234</font></li> </ul> <blockquote><blockquote><p><font size="4">Bolos of Mendez in 200 BC describes methods for producing false silver:</font></p><p><font size="4"><i>"About the making of “uncoined”: the quicksilver from arsenic, or sandarach, as you prefer, cook it as usual, deposit it on copper or coppered iron, and it will be whitened. Whitened magnesia does the same thing, and transmuted arsenic, and cooked cadmia (ZnO?], and unfired sandarach and whitened pyrite, and psimuthion [lead acetate] cooked with sulfur."</i></font></p></blockquote></blockquote><p> <ul> <li><font size="4"><a href="https://warwick.ac.uk/fac/arts/classics/staff/butcher/debasement_and_decline.pdf" target="_blank" class="externalLink ProxyLink" data-proxy-href="https://warwick.ac.uk/fac/arts/classics/staff/butcher/debasement_and_decline.pdf" rel="nofollow">Butcher, Kevin </a> (2015) <i>Debasement and the decline of Rome.</i> In: Bland, Roger and Calomino, Dario, (eds.) Studies in ancient coinage in honor of Andrew Burnett. London: SPINK, pp. 181-205. ISBN 9781907427572</font></li> </ul><p>[/QUOTE]</p><p><br /></p>
[QUOTE="Sulla80, post: 3954019, member: 99456"]While I will claim interest, it is as a collector, and non-expert that I share the following. Other references, additions, corrections always appreciated. [B]Timing:[/B] Here's a graph of the table in [URL='https://smile.amazon.com/gp/offer-listing/0801852919/ref=tmm_hrd_used_olp_sr?ie=UTF8&condition=used']Harl[/URL] (Ch. 6 - The Great Debasement and Reform A.D. 193-305 Table 6.2 p 130) [ATTACH=full]1041594[/ATTACH] And another graph from [URL='https://www.jstor.org/stable/10.2307/42663317']G. C. Haines 1941[/URL] illustrating data from [URL='http://numismatics.org/zfn/38060000322628/125297.pdf']J. Hammer [/URL](1908) the decline in silver content over time - more recent studies and techniques for analyzing the silver content may have improved on this view. [ATTACH=full]1041588[/ATTACH] Here is a [URL='http://money.visualcapitalist.com/deaths-roman-emperors-vs-silver-coin-content/']prettier graph[/URL] with a less clear source of data. [B]Process:[/B] There were multiple processes potentially used to make plated counterfeit and official coins throughout time. While there are several candidates for silver plating in ancient Rome, there is uncertainty about the process used for late Roman coins. Here are several candidates (there are others mentioned in the references below): [LIST] [*][B]"diffusion bonding" or "Sheffield plating" [/B]: silver copper sheets heated together reported in use for Roman Republican fourrée denarii, wrap copper flan in a silver foil and heat. This is considered too labor intensive to have been used at scale in late roman empire [*][B]"dipping in silver chloride" [/B]- Blanks were maintained hot, dipped in molten silver chlorides, and quenched in a bath [*][B][B]"mercury silvering", "amalgam plating", or "fire gilding"[/B] -[/B] a good way to get mercury poisoning - dissolve silver in mercury, then spread on the flan like peanut butter, then evaporate the mercury with heat, this technique is mentioned as a possibility for late roman coins. [*][B]"depletion silvering", "pickling" or "blanching" [/B]- take a copper-silver alloy - use citric acid or vinegar to leach out the copper and enrich silver content of the outer surface, then strike to produce a silver surface plating which seems to be a leading hypothesis for later Roman coins. [/LIST] Selected references for further reading: [LIST] [*][SIZE=4][URL='https://www.worldcat.org/title/coinage-in-the-roman-economy-300-bc-to-ad-700/oclc/33817980']Harl, K. W.[/URL] (1996). [I]Coinage in the Roman economy, 300 B.C. to A.D. 700[/I]. Baltimore: Johns Hopkins University Press[/SIZE] [*][SIZE=4][URL='http://www.jstor.org/stable/42663317']Haines, G. C.[/URL] (1941). THE DECLINE AND FALL OF THE MONETARY SYSTEM OF AUGUSTUS. [I]The Numismatic Chronicle and Journal of the Royal Numismatic Society,[/I] [I]1[/I](1/2), 17-47[/SIZE] [*][SIZE=4][URL='https://doi.org/10.1017/S0003581500070335']Susan La Niece[/URL] (1990) Silver Plating on Copper, Bronze and Brass. [I]The Antiquaries Journal,[/I] [I]70[/I](1), 102-114. doi:10.1017/S0003581500070335[/SIZE] [*][SIZE=4][URL='http://researchonline.ljmu.ac.uk/id/eprint/5590/1/373706.pdf']Cope, L. H.[/URL] , (1974) “The metallurgical development of the Roman Imperial coinage during the first five centuries A.D.”, PhD Thesis, Liverpool Polytechnic, Liverpool John Moores University. doi:10.24377/LJMU.t.00005590[/SIZE] [*][SIZE=4][URL='https://www.forumancientcoins.com/historia/Silvering%20on%20Roman%20coins.pdf']C. Vlachou, J.G. McDonnell, R.C. Janaway[/URL] (2002) Experimental investigation of silvering in late Roman coinage, Mat. Res. Soc. Symp. Proc. Vol. 712[/SIZE] [*][SIZE=4]Pliny describes a technique for plating in [URL='http://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.02.0137:book=34:chapter=48&highlight=plating']Naturalis Historia book 34 ch. 48.[/URL][/SIZE] [*][SIZE=4][URL='http://www.jstor.org/stable/43580265']Keyser, P. [/URL](1995). GRECO-ROMAN ALCHEMY AND COINS OF IMITATION SILVER. [I]American Journal of Numismatics (1989-),[/I] [I]7/8[/I], 209-234[/SIZE] [/LIST] [INDENT][INDENT][SIZE=4]Bolos of Mendez in 200 BC describes methods for producing false silver: [I]"About the making of “uncoined”: the quicksilver from arsenic, or sandarach, as you prefer, cook it as usual, deposit it on copper or coppered iron, and it will be whitened. Whitened magnesia does the same thing, and transmuted arsenic, and cooked cadmia (ZnO?], and unfired sandarach and whitened pyrite, and psimuthion [lead acetate] cooked with sulfur."[/I][/SIZE][/INDENT][/INDENT] [LIST] [*][SIZE=4][URL='https://warwick.ac.uk/fac/arts/classics/staff/butcher/debasement_and_decline.pdf']Butcher, Kevin [/URL] (2015) [I]Debasement and the decline of Rome.[/I] In: Bland, Roger and Calomino, Dario, (eds.) Studies in ancient coinage in honor of Andrew Burnett. London: SPINK, pp. 181-205. ISBN 9781907427572[/SIZE] [/LIST][/QUOTE]
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