Question About Cleaning Coins

When looking for varieties, it is very hard to see them when the coin is very dirty and gritty. I also was told by one of the grading services, to rinse the coin lightly in soap and water to remove the dirt and grit. I was told this would not effect the grade of my coin, well my AU coin came back from them AU details- XF-40 "cleaned", unfortunatly sometimes you have to learn the hard way.
They are better left alone.

I have done a series of tests on a proof modern coin in 9999 gold
The results were evaluated with an Eschenbach 10X LED loupe whose manufacturer happens to be german (nextdoor neighbour to belgium)
and recommended by ND
First series acetone, methylethylketon, toluene, ethylacetate,
No visual difference
Second series of test with thinner, petrol, airbrush cleaner,white spirit ( all oily waterrepulsing )
In this series water cleaning was necessary and then a quick dip in acetone when the coin was still waterwet to remove any drying spots
Then the last test was rubbing liquid babysoap on the coin under water with the thumbs , washing and acetone dip and dry
Since it was a proof to start with no difference was visible in shine
surprisingly neighter on the die sandblasted matte devices )
When the heatwave here is over I may try the acids although I am not to keen on acids which may attack copperconcentrations or silver surface contamination
By way of a safety data sheet I found that jewellers use phosphoric acids and ureum and surface tension reducers
( I am a chemical engineer so I understand all the dangers of fire, explosion, burning my fingers and asphixation and cancer risks
I have a very powerfull windowventilator and a carboncanister gasmask together with all resistent gloves and of course gogles so if you want to experiment read the safety data sheets , ventilate, use carbon canister gasmask and gloves )
And yes our leading coinvendor rightly claims he can recognise an old napoleon which has been soap cleaned

After reading some of the responses, I am glad I asked about this. It really sounds harmless, but I think I've decided to leave these coins in their "natural" state Thanks to all for the helpful advice. John

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Originally posted by Mike

Hi ageka, how have cleaning experiments gone on other compositions? Have you done any on silver or copper? I think gold would be the most impervious to damage from mild chemicals. Thanks, Mike

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Hi Mike
All the products I used are solvents
water mixable or oily like
Every solvent has unique properties
I never had a coin with pvc plasticizer goo on it
so I never tried acetone on silver or copper
It has been reported to me that fake patina can come off
silver or copper ; real patina should be untouched by acetone
I had three kind of problems sofar
1) Fresh fringerprints on gold
acetone will take those off in 10 seconds
2) Gold coins which had been glued onto thick paper as a collecting method
Since it was oldfashioned arabica gum it came off in acetone in 30 seconds
Acetone has the advantage that on a hot day it dries off in less then 5 seconds without any residue seen by a 10X magnification
3) I now have a 9999 fine coin with a dozen red spots
since it came in a red lacquered box I presumed paint or deye
but non of the solvents did any good
It may still be a heatfixed type of paint (like acrylic) so I will get me some industrial paintstripper
It may also be silversulfide since a german forum reported there have been problems with 9999 proof blanks containing microthin contamination of silver and the black sulfide is so thin it looks red on goldcoins ( it seems the german mint is willing to replace the coins involved )
August