What does this sentence mean?

Jenkinson   Fri Jun 01, 2007 1:53 am GMT
The golden rule is never to clean a valuable coin.
Guest   Fri Jun 01, 2007 2:56 am GMT
The golden rule is ~ the important thing is
Anwar Gul Jala Bela   Fri Jun 01, 2007 6:38 am GMT
I think it means to be natural in your actions and thoughts.
Great people are great because they have their own point of view regarding every thing.
myself   Fri Jun 01, 2007 9:14 pm GMT

Just have a look at the following link :


It will help you not to clean everything in life.

All the best. myself
Jenkinson   Mon Jun 04, 2007 1:39 am GMT
I know what "the golden rule" means. The key point is the latter "never to clean a valuable coin". Should "clean a valuable coin" be literally understood? I am still not quite clear about what the sentence wants to say.
Uriel   Mon Jun 04, 2007 2:07 am GMT
Cleaning or repairing antiques often diminishes their value, because it may actually damage them. Patinas and natural corrosion can also be a key to determining the age of an item like a coin, especially it if was struck before dates were commonly stamped on coins, or if there is reason to question its authenticity. If you have something really old or valuable, you're usually better off taking it to an expert for appraisal and restoration, rather than trying to do it yourself and screwing something up.
exCoinCollector   Mon Jun 04, 2007 3:00 am GMT
Generally speaking, a coin in "pristine", uncleaned, original condition is worth more than one that's been cleaned. Long ago, cleaning wasn't frowned upon so much (coins in the US mint collection were even cleaned periodically), so old US coins that haven't been cleaned are often hard to find (1795 dollars, for example), so they're worth more.

Cleaning can also leave hairlines on the coin's surface, and these can reduce the value considerably (especially for a proof or high grade uncirculated coin). Even dipping to remove the tarnish can often result in unnatural-appearing surfaces, especially for copper coins. After many years, a dipped coin may eventually look better, but they're still not "original", and are sometimes described as "retoned, after old dipping/cleaning".

That being said, sometimes a dirty coin (with grease, fingerprints, PVC residue, etc.) should be swished in a neutral organic solvent to remove the grease, which can lead to eventual corrosion. They (and I) used to use a freon-like chemical to safely remove surface grime, but leave all toning intact. I don't know what they use today.
Jenkinson   Mon Jun 04, 2007 5:57 am GMT
Particular thanks to Uriel, exCoinCollector for your illuminating explanations.
Uriel   Mon Jun 04, 2007 6:47 am GMT
We live to serve! ;)