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<p>[QUOTE=&quot;MrSpud, post: 110985, member: 4621&quot;]You probably accidently artificially toned the coin when you heated it in the oven. Heat does funny things to the color of coins. You can produce thin oxidation films of different colors by heating coins and they can take on different characteristcs depending on what is in the air around the coin when it is heated. For example, below are pictures of the same coin being heated in the presence of copper. The pictures were taken approximately every 10 seconds as the coin was being heated. Notice how the color changes as the coin is left on heat? That&#039;s cause the thermal oxidation film is getting thicker.</p><p><br /></p><p><img src="http://nexus.mythicdesigns.net/spudcoins/TonedProgressionAT3.jpg" class="bbCodeImage wysiwygImage" alt="" unselectable="on" /></p><p><br /></p><p>This is called artificial toning or accelerated toning and is looked down on if it is done to fool people into thinking the coin is more valuable. Coins can also tone naturally over time due to interactions with atmospheric sulfides or other chemicals that the coin gets accidently exposed to. For example, here is a picture of a naturally toned lincoln cent where part of the coin has toned silver.</p><p><br /></p><p><img src="http://nexus.mythicdesigns.net/spudcoins/11.11Linc44SToned.jpg" class="bbCodeImage wysiwygImage" alt="" unselectable="on" /></p><p><br /></p><p>As for cleaning and retoning a copper cent here is a link to a kids experiment page that shows you an effective way to clean pennies <a href="http://www.infoage.org/webpages/kexperiments.html" target="_blank" class="externalLink ProxyLink" data-proxy-href="http://www.infoage.org/webpages/kexperiments.html" rel="nofollow">http://www.infoage.org/webpages/kexperiments.html</a> </p><p>Just be sure to rinse the pennies with running tap water after you clean them with this technique or they will turn green from the salt residue.</p><p><br /></p><p>To make the pennies brown again, just get some vaseline and sulfur. You get about a gram of vaseline and thoroughly mix in a tiny amount of powdered sulfur (available at the drug store called Flowers of Sulfur). You want to use an extremely small amount of the powdered sulfur or the coin will turn almost black. Well, anyway, you thoroughly mix in the sulfur powder into the vaseline and then take a little bit and rub it on the coin. When the coin starts to turn brown, wipe off the excess vaseline with a paper towel. Then wash it with soap and water or wipe it off with rubbing alcohol. It will turn brown right away. If it turns too dark too quick, just take a little dab of the vaseline/sulfur and mix it into another gram or so of pure vaseline to dilute it out and try again on the next one. The coin turns brown because a film of brown copper sulfide forms on the surface of the coin.</p><p><br /></p><p>Just don&#039;t use these techniques to try and make coins look more valueable than they are with the intent of selling them. You will just end up with a bad reputation if you do and noone will trust you. It is perfectly fine to experiment to gain knowledge of chemistry and metallurgy though.</p><p><br /></p><p>Also, have fun, but be safe. Only do these kinds of experiments with adult supervision.[/QUOTE]</p><p><br /></p>

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