Yellow deposit on low content silver

[Figleaf]

unfortunately for me, my go-to vendor for this type dispenses most coins (Sri Ha) seemingly coated with a yellowish (Golden?) sheen

This may be a chemical residue of bleached paper. The discolouring can probably be removed with acetone. Acetone does not react with metal. Still, it is a good idea to neutralise the coin with lukewarm, soapy water. Dry well, e.g. in full sunshine or above a central heating element.

Peter

[Amit Kher]

This may be a chemical residue of bleached paper. The discolouring can probably be removed with acetone. Acetone does not react with metal. Still, it is a good idea to neutralise the coin with lukewarm, soapy water. Dry well, e.g. in full sunshine or above a central heating element.

Peter

thanks Peter, i remembered your suggestion about acetone from a previous post and have used it with partial success

[THCoins]

Yes, one has to be carefull with cleaning ancients. In the past i used a very effective cleaning and lubricating oil to clean surfaces. Only downside was that it made my coins get a bit purple sheen which was even exagerated on photos. It is a process of trial and error.

[Figleaf]

thanks Peter, i remembered your suggestion about acetone from a previous post and have used it with partial success

Acetone is pretty good with chemicals. However, chemicals may react with metal, rendering acetone ineffective. You can still clean the residual deposits if you wish, but the chemicals will probably have eaten into the metal. On a modern proof, this is lethal. On a highly worn, common antique coin, who cares for a tad more damage if it improves the coin's looks?

Try lemon or lime juice. Dilute with water. If ineffective, use less water until you are happy. Some members have reported success with a long soak. I prefer to stay with the coin, especially if it has low silver content. Make sure to neutralise with plenty soap and water and dry well. The coin's patina is likely to suffer and that is your risk and responsibility. Do not use this treatment on copper or bronze coins. They may become purple and I know of no way to rectify that.

An alternative (in particular for coppers and bronzes) is electrolysis, but it's more difficult to set up. Search this site for more info.

Peter

[Amit Kher]

i've used distilled natural vinegar diluted with distilled water on both silver and copper/ bronze coins, mainly to get rid of encrustations and usually only if some identifying feature is obscured; and a mild rubbing with cotton ear buds if required
there were few damages but mostly i was able to get what i was looking for;
after this process a 15-20 minute dip in acetone to remove any residual moisture.
a calculated risk, if it isn't an expensive ancient and identity is hampered by encrustation, then perhaps worth a try
unfortunately i haven't saved before-cleaning images, else would have shared with post-cleaning results

[Amit Kher]

just found a before-after image set

[Figleaf]

When you have decided to clean, it is very important to know what you want to remove and what that stuff has settled on.

From the second picture, it seems that this is a low silver content coin, but the lighting may have played tricks. From the upper picture, the coin looked coppery. If the difference in lighting is not deceiving me, it seems like you wanted the original metal colour to come out. Sorry if that is not the case, but I can only work with what I know.

From the treatment you decided on, it looks like you thought the coin was covered by hardened mud, because water will solve mud. You could have added soap, because soap solves fatty substances, regularly part of mud, but so far so good.

Using acetone makes sense, because mud often contains chemicals and water may not remove it. However, AFAIK, acetone does not react with water. It vaporises quickly, but that doesn't remove water, which also vaporises, but more slowly. Therefore, the coin should still be dried.

If you wanted thorough and deep cleaning, you could have used ultra-sound cleaning. Ultra-sound cleaners are not very expensive any more and as a bonus, they also work on spectacles and jewellery.

Where our ways part is the vinegar. Even diluted, this is an acid. Acids should be used only as a last resort, because they remove metal.

I assume you showed the second picture because you were happy with the outcome. That's fine for you, but you ran a risk by using vinegar, as it could have reacted with the copper, making it look purple.

The bottom line on running risk is that you should only run it when you are adequately compensated for it, e.g. you want to sell a coin worth 100. You estimate that by using an acid successfully, you can raise the price to 150, but you run the risk of losing the coin altogether. If you think chances of success are 80%, a lot of say 10 such coins would be worth 10 x 100 = 1000 before conservation and 8 x 150 = 1200 after conservation. If you are not selling, try expressing your satisfaction with the coin before and after in points and use the same analysis. The learning points of this little model are that it pays to know what you are doing and why you are doing it.

Peter

[Amit Kher]

thanks Peter for the detailed reply; point taken

trying to answer some questions in your response -
it's a coin from a series known with low silver content

what i'd wanted was to clean the area in front of the bust because what was partially visible wasn't corresponding with any of the known patterns; it did get cleared up and incidentally uncovered features that i haven't seen in any other coin, as yet

soap definitely will be added, if and when i venture into something similar again

a few times i've substituted isopropyl alcohal in place of acetone, i think it doesn't evaporate as quickly; i do cover the container when using acetone to retard the evaporation

i've earlier used Ultra-sound with copper coins, unfortunately presently it's not available, but will try to get my hands on one again

sometime back i'd read a post by Bruce, where he suggested - "dry the coins, and soak in 100% Isopropyl alcohol, for about 20 minutes. This will help draw  out more water from the coin fabric."
as a trial i used acetone instead as it's supposed to be organic

as i haven't indulged in selling coins, that calculation has never been a part of my 'experiments'

i experimented with mostly very low cost coins, mainly with the purpose of identifying and yes i was always aware of the risk of totally losing it, which i did occasionally

but yes, i'm always open to corrections and will keep your suggestions in mind when i go experimenting again