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<p>[QUOTE=&quot;Oldhoopster, post: 5318026, member: 84179&quot;][USER=27832]@-jeffB[/USER] the authors of the Stony Brook Univ paper are only proposing a mechanism.&nbsp; What we do know from their paper is that in the presence of light and moisture, AFTER the acetone evaporated 18 hrs later, copper acetate crystals formed on a 100% copper foil.&nbsp; </p><p><br /></p><p>I think their proposed mechanism of Cu being a catalyst that helps acetone break down into acetic acid is valid.&nbsp; What they don&#039;t say is when does this reaction occur and what are the concentrations.&nbsp; </p><ul> <li>Is it immediately upon immersion?&nbsp; </li> <li>Is the concentration of acetic acid high at the beginning, or after 18 hrs as the acetone is just about completely evaporate? </li> <li>At what point does the copper acetate form?&nbsp; This is a big thing because it&#039;s the part where Cu from a coin can can physically become involved in the reaction.&nbsp; </li> <li>How do the conditions of the experiment relate to numismatic usage? The experiment used a static sample.</li> <li>If I stir or swirl the acetone container or coin, will there be enough acetic acid to concentrate near the coin surface or will it be quickly diluted into the solvent?</li> </ul><p>I think the research is solid and their proposal is reasonable, but most collectors don&#039;t let their coin sit out long enough for the acetone evaporate.&nbsp; Nothing in that paper suggests that a short soak and rinse will lead to the formation of concentrated acetic acid.</p><p><br /></p><p>I believe the members who have posted that they have had copper change color after soaking in acetone.&nbsp; But I feel that it&#039;s more likely due to technique (soaking too long, improper rinsing, redeposited organic residue) or a questionable surface under the residue.&nbsp; So far, the science doesn&#039;t support acetone being a problem for copper if used for a short soak and rinse.</p><p><br /></p><p>I&#039;ve soaked hundreds of copper coins over the years (primarily as a precaution to remove PVC plastic over residue) and have had the same results as you [USER=27832]@-jeffB[/USER] no discoloration[/QUOTE]</p><p><br /></p>

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