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.mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">For 1924 silent film, see <a href="/wiki/Tarnish_(film)" title="Tarnish (film)">Tarnish (film)</a>.</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Wolfram_evaporated_crystals_and_1cm3_cube.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Wolfram_evaporated_crystals_and_1cm3_cube.jpg/290px-Wolfram_evaporated_crystals_and_1cm3_cube.jpg" decoding="async" width="290" height="158" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Wolfram_evaporated_crystals_and_1cm3_cube.jpg/435px-Wolfram_evaporated_crystals_and_1cm3_cube.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Wolfram_evaporated_crystals_and_1cm3_cube.jpg/580px-Wolfram_evaporated_crystals_and_1cm3_cube.jpg 2x" data-file-width="5472" data-file-height="2988" /></a><figcaption><a href="/wiki/Tungsten" title="Tungsten">Tungsten</a> rods with evaporated crystals, partially <a href="/wiki/Redox" title="Redox">oxidized</a> with colorful tarnish</figcaption></figure> <p><b>Tarnish</b> is a thin layer of <a href="/wiki/Corrosion" title="Corrosion">corrosion</a> that forms over <a href="/wiki/Copper" title="Copper">copper</a>, <a href="/wiki/Brass" title="Brass">brass</a>, <a href="/wiki/Aluminum" class="mw-redirect" title="Aluminum">aluminum</a>, <a href="/wiki/Magnesium" title="Magnesium">magnesium</a>, <a href="/wiki/Neodymium" title="Neodymium">neodymium</a> and other similar <a href="/wiki/Metals" class="mw-redirect" title="Metals">metals</a> as their outermost layer undergoes a chemical reaction.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> Tarnish does not always result from the sole effects of oxygen in the air. For example, silver needs <a href="/wiki/Hydrogen_sulfide" title="Hydrogen sulfide">hydrogen sulfide</a> to tarnish, although it may tarnish with oxygen over time. It often appears as a dull, gray or black film or coating over metal. Tarnish is a surface phenomenon that is self-limiting, unlike <a href="/wiki/Rust" title="Rust">rust</a>. Only the top few layers of the metal react. The layer of tarnish seals and protects the underlying layers from reacting. </p><p>Tarnish preserves the underlying metal in outdoor use, and in this form is called chemical <a href="/wiki/Patina" title="Patina">patina</a>.<sup id="cite_ref-:0_2-0" class="reference"><a href="#cite_note-:0-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Unlike wear patina necessary in applications such as copper roofing, outdoor copper, bronze, and brass statues and fittings, chemical patina is considered a lot more uneven and undesirable.<sup id="cite_ref-:0_2-1" class="reference"><a href="#cite_note-:0-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> Patina is the name given to tarnish on copper-based metals, while <a href="/wiki/Toning_(coin)" title="Toning (coin)">toning</a> is a term for the type of tarnish which forms on coins. </p> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:1899_reverse.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/3/30/1899_reverse.jpg/220px-1899_reverse.jpg" decoding="async" width="220" height="219" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/3/30/1899_reverse.jpg/330px-1899_reverse.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/3/30/1899_reverse.jpg/440px-1899_reverse.jpg 2x" data-file-width="764" data-file-height="761" /></a><figcaption>A <a href="/wiki/Morgan_dollar" title="Morgan dollar">Morgan dollar</a> demonstrating a colourful form of <a href="/wiki/Toning_(coin)" title="Toning (coin)">toning</a> on its reverse. While tarnishing on other metal objects is generally cleaned off, some toning on coins may be considered aesthetically pleasing or beneficial to the coin's value, and is therefore kept <i>in situ</i>.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></figcaption></figure> <div class="mw-heading mw-heading2"><h2 id="Chemistry">Chemistry</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Tarnish&action=edit&section=1" title="Edit section: Chemistry"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Tarnish is a product of a <a href="/wiki/Chemical_reaction" title="Chemical reaction">chemical reaction</a> between a <a href="/wiki/Metal" title="Metal">metal</a> and a <a href="/wiki/Nonmetal_(chemistry)" class="mw-redirect" title="Nonmetal (chemistry)">nonmetal</a> <a href="/wiki/Chemical_compound" title="Chemical compound">compound</a>, especially <a href="/wiki/Oxygen" title="Oxygen">oxygen</a> and <a href="/wiki/Sulfur_dioxide" title="Sulfur dioxide">sulfur dioxide</a>. It is usually a metal <a href="/wiki/Oxide" title="Oxide">oxide</a>, the product of <a href="/wiki/Oxidation" class="mw-redirect" title="Oxidation">oxidation</a>; sometimes it is a metal sulfide. The metal oxide sometimes reacts with water to make the hydroxide, or with carbon dioxide to make the carbonate. It is a chemical change. There are various methods to prevent metals from tarnishing. </p> <div class="mw-heading mw-heading2"><h2 id="Prevention_and_removal">Prevention and removal</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Tarnish&action=edit&section=2" title="Edit section: Prevention and removal"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Using a thin coat of <a href="/wiki/Polishing" title="Polishing">polish</a> can prevent tarnish from forming over these metals. Tarnish can be removed by using <a href="/wiki/Steel_wool" title="Steel wool">steel wool</a>, <a href="/wiki/Sandpaper" title="Sandpaper">sandpaper</a>, <a href="/wiki/Emery_paper" class="mw-redirect" title="Emery paper">emery paper</a>, <a href="/wiki/Sodium_bicarbonate" title="Sodium bicarbonate">baking soda</a> or a <a href="/wiki/File_(tool)" title="File (tool)">file</a> to rub or polish the metal's dull surface. Fine objects (such as silverware) may have the tarnish electrochemically reversed (non-destructively) by resting the objects on a piece of aluminium foil in a pot of boiling water with a small amount of salt or baking soda,<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> or it may be removed with a special polishing compound and a soft cloth. Gentler abrasives, such as <a href="/wiki/Calcium_carbonate" title="Calcium carbonate">calcium carbonate</a>, are often used by museums to clean tarnished <a href="/wiki/Silver" title="Silver">silver</a> as they cannot damage or scratch the <a href="/wiki/Silver" title="Silver">silver</a> and will not leave unwanted residues.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Tarnish&action=edit&section=3" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFRevieUhlig2008" class="citation book cs1">Revie, R. Winston; Uhlig, Herbert Henry (2008). <i>Corrosion and corrosion control: an introduction to corrosion science and engineering</i> (4th ed.). Hoboken, N.J: Wiley-Interscience. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-471-73279-2" title="Special:BookSources/978-0-471-73279-2"><bdi>978-0-471-73279-2</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Corrosion+and+corrosion+control%3A+an+introduction+to+corrosion+science+and+engineering&rft.place=Hoboken%2C+N.J&rft.edition=4th&rft.pub=Wiley-Interscience&rft.date=2008&rft.isbn=978-0-471-73279-2&rft.aulast=Revie&rft.aufirst=R.+Winston&rft.au=Uhlig%2C+Herbert+Henry&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATarnish" class="Z3988"></span></span> </li> <li id="cite_note-:0-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-:0_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:0_2-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://www.riogrande.com/knowledge-hub/guide-to-tarnish/">"Guide to Tarnish"</a>. <i>Rio Grande</i>. 2019-08-14<span class="reference-accessdate">. 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Retrieved <span class="nowrap">1 April</span> 2019</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=The+Spruce+Crafts&rft.atitle=Coin+Toning%3A+Definition%2C+Discussion+and+Effect+on+Value&rft.aulast=Bucki&rft.aufirst=James&rft_id=https%3A%2F%2Fwww.thesprucecrafts.com%2Fcoin-toning-definition-768303&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATarnish" class="Z3988"></span></span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20160331180638/http://www.philamuseum.org/booklets/7_44_85_1.html?page=2">"Finishing techniques in Metalwork"</a>. <i>philamuseum.org</i>. <a href="/wiki/Philadelphia_Museum_of_Art" title="Philadelphia Museum of Art">Philadelphia Museum of Art</a>. 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Retrieved <span class="nowrap">2012-10-19</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=scifun.chem.wisc.edu&rft.atitle=Remove+Tarnish+from+Silver&rft_id=http%3A%2F%2Fscifun.chem.wisc.edu%2Fhomeexpts%2FTARNISH.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATarnish" class="Z3988"></span></span> </li> <li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20120323201653/http://ohiohistory.wordpress.com/2011/06/02/making-it-shine/">"Making it Shine"</a>. <i>ohiohistory.wordpress.com</i>. <a href="/wiki/Ohio_Historical_Society" class="mw-redirect" title="Ohio Historical Society">Ohio Historical Society</a>. 2011-06-02. Archived from <a rel="nofollow" class="external text" href="http://ohiohistory.wordpress.com/2011/06/02/making-it-shine/">the original</a> on 2012-03-23<span class="reference-accessdate">. Retrieved <span class="nowrap">2012-10-19</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=ohiohistory.wordpress.com&rft.atitle=Making+it+Shine&rft.date=2011-06-02&rft_id=http%3A%2F%2Fohiohistory.wordpress.com%2F2011%2F06%2F02%2Fmaking-it-shine%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3ATarnish" class="Z3988"></span></span> </li> </ol></div></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Tarnish&oldid=1258161563">https://en.wikipedia.org/w/index.php?title=Tarnish&oldid=1258161563</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/wiki/Category:Chemical_reactions" title="Category:Chemical reactions">Chemical reactions</a></li><li><a href="/wiki/Category:Metals" title="Category:Metals">Metals</a></li><li><a href="/wiki/Category:Metalworking_terminology" title="Category:Metalworking terminology">Metalworking terminology</a></li><li><a href="/wiki/Category:Corrosion" title="Category:Corrosion">Corrosion</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_is_different_from_Wikidata" title="Category:Short description is different from Wikidata">Short description is different from Wikidata</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 18 November 2024, at 13:06<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. 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