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- - ultrasonic jewery cleaner for coins? (http://goldismoney.info/forums/showthread.php?t=45603)

grizzlyduck | 07-13-2006 08:53 PM
ultrasonic jewery cleaner for coins? just wondering if one of those ultrasonic cleaners for jewelery would work for coins. i have some 90% that isn't numismatic that i would like to clean. has anyone tried this?

didgmike | 07-13-2006 10:02 PM
Re: ultrasonic jewery cleaner for coins? i used an 80's vintage high-power u-s cleaner and a new, high power super dooper u-s cleaner on various silver coins a few months ago at my work. We use them there to clean surgical instruments in preparation for autoclaving......so i figured it would work on the coins just fine.... it did.....though not with, WOW! results. The "super nasty" coins improved to "slightly nasty" coins. The "pretty good" coins were upgraded to " pretty, pretty good" coins. not worth my time and effort to do it again :smokin: , but it works.

goldminer | 07-14-2006 06:44 AM
Re: ultrasonic jewery cleaner for coins? A lot of people think it's a waste of time, money, and a VERY bad idea, to clean 90%. Obviously worn coins that are shiney look like there's something wrong with them...they appear too far out from the "norm" which may cause someone who is not overly familiar with 90% to in a shtf environment, be frightened bytheir appearance and refuse to accept them. Too, what is gained by investing in the process? All the cleaning in the world will not increase a coins value a single cent. Suggestion: clean one worn coin and look at it.

Au_Ag | 07-14-2006 09:32 AM
Re: ultrasonic jewery cleaner for coins? The little 10 or 15 buck deal from K-mart worked fine on some older gold coins. I put in warm water, added a little lemon juice, vibrated for 30 min and turned them over and repeated. It softened the crud enough to where lightly buffing by hand with a soft cloth removed the remaining crud. These gold bullion coins were over 100 years old and looked pretty funcky. They looked really good after this procedure. I could only do four or five coins at a time, for fear of them wearing a bright spot from contact. No way I would try to do a lot of 90% with the procedure I used - too time consuming.

latecomer | 07-14-2006 10:17 AM
Re: ultrasonic jewery cleaner for coins? For cleaning silver coins, very high power is needed to produce satisfactory results. The small "jewellery" type cleaners will do little more than rubbing with a soft cloth and a bit of detergent. (If some microscopic abrasion is not an issue, the fastest way to clean a silver coin is to rub it with a wad of cotton moistened with a paste made from floated chalk.) I believe that, with gold and lemon juice the ultrasonic performs well, since gold corrodes to produce water soluble compounds and copper compounds are soluble in citric acid. For cleaning old tarnished 90%, this sequence works best for me: 1) The aluminum+soda+salt method. At this point the apearance will not be much improved yet, but it removes the silver sulfide component from the crust, weakening it. This must not be "overdone" to the point of completely disintegrating the aluminum foil or a very sturdy coating of aluminum oxides will form. Foil must be in contact with all coins during the process. 2) Brief (10 min.) boiling in battery (38%) sulfuric acid, followed by a day or two of "pickling" in the same. This will not harm the silver, but will dissolve most of the tarnish. After this I put the coins in ziplock bags with the same 38% acid and place the (sealed) bags under water in the ultrasonic cleaner. Run it for about 1/2 hour. At this point almost no tarnish is noticeable even in the most problematic locations (like deep edge inscriptions). What tarnish remains is usually yellow, not black. Note: Do not use acidic media directly in the ultrasonic. A stainless one will get corroded and an aluminum one likely totally destroyed. Also, do not use anything containing the chloride ion (salt, bleach, ...) but the operating manuals usually warh against that. 3) Depending on the particular alloy, I either repeat step 1), or 2) - but with a mixture of thiourea + sulfuric acid in the bags. Or both (in that sequence). At this point no remaining tarnish is noticeable. 4) Brief boiling in weak sulfuric or conc. citric acid (to remove either aluminum oxides or excess thiourea). 5) Washing with distilled water (to prevent splash marks) and drying. Do not expect to get a shiny surface by cleaning a worn coin. It will rather resemble the appearance of worn aluminum utensils. To get a mirror finish, mechanical polishing is necessary to flatten out the surface (using say chalk or rouge as medium and either a sander/polisher or a polishing pad in an electric drill). However, on close inspection tiny unpolished margins around letters and other raised areas reveal what has been done...

latecomer | 07-14-2006 11:37 AM
Re: ultrasonic jewery cleaner for coins? The result will not be impeccable, but this is the only method I've found so far that really works on 90% (as well as some lower purities) and doesn't require mechanical cleaning of every coin. So it can be scaled up to process large quantities. Every coin will benefit from some light polishing afterwards, just rubbing between fingers with some chalk "mud" works wonders. Of course, this is for bullion only, not numismatics... I stick to floated chalk, because it has the right particle hardness (about equal to pure copper and therefore softer than alloyed coins). "Floated" is important... Ordinary chalk powder has silica in it (sand and dust) that makes bad scratch marks.

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