DeoxIT® Penny Experiment

I got a DeoxIT pen and the package claims to remove oxidation unlike other products. I tested the product on a dull penny following the directions. The penny would look shiny if the oxidation was removed, but it stays dull. Why is this?

Thanks
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The DeoxIT® will remove the oxidation on the penny, but you will need to be patient. Let it sit overnight, wipe with a cloth or tissue, and you will notice green copper oxides. It is non-aggressive to metals, and is formulated to remove oxidation, but more importantly, it improves the signal transfer. For additional information, please go to the link entitled "Why DeoxIT® is Different" at: http://store.caig.com/s.nl/it.I/id.22/.f?sc=17&category=-117