World of Coins

Collecting coins => Cleaning, conservation and storage => Topic started by: Abhay on October 10, 2012, 11:46:41 AM

Title: Cleaning Silver coins with Brasso
Post by: Abhay on October 10, 2012, 11:46:41 AM
Often, we get Silver coins, covered with Black Dirt and Grease, which look unattractive. They also hide the details on the coins.

I generally use Brasso (http://en.wikipedia.org/wiki/Brasso), to remove the grease and dirt on the coins.

Is it OK to use Brasso to remove the grease on the coins? Generally, I have seen that if there was any Patina on the coin, the patina is also removed from the coin. So, I never use it for the old coins, having Patina on them.

An example is shown here, for the Victoria queen coin.

Your comments please.

Abhay

(The Coin to the left is the cleaned one)
Title: Re: Cleaning Silver coins with Brasso
Post by: Figleaf on October 10, 2012, 12:10:17 PM
Brasso is an abrasive product. It achieves its effect by removing the upper part of the silver. Yes, it will get rid of sediments, but at the cost of dulling of the image that cannot be repaired. It also gives an unnatural, bluish shine, but with time and pollution, that will go away.

There is a whole arsenal of techniques that are not abrasive available for cleaning silver coins. Which one is the most proper depends on what you want to clean away, so determining what is on your coin is key. It looks like your Victorian rupee was covered with a mixture of solidified dust and oxydation (the black parts remaining after the Brasso treatment.) The dust may be solved with water and soft soap. Silver oxyde is hard to remove without abrasives. If the dirt does not react to water and soap, Bruce's magic soda potion could have helped.

Peter
Title: Re: Cleaning Silver coins with Brasso
Post by: Coinsforever on October 10, 2012, 02:31:47 PM
Usually I have seen brasso at all handicraft showrooms selling brass idols , dishes & other brass artifacts.

As the name itself is self explanatory brasso is normally used for purpose of cleaning brass metal products  . I'm not sure if recommendation given on the container of brasso to clean silver articles as well.


Cheers ;D
Title: Re: Cleaning Silver coins with Brasso
Post by: aarkay on October 10, 2012, 04:46:53 PM
Hi…

Yes….. Brasso is for brass articles….but for cleaning silver idols, lamps etc. I use any ordinary tooth powder like Colgate….it gives good results…I have tried it on British India silver coins…it works and there are no scratches as the powder is silky smooth…better to test clean on a not so valuable silver coin and see the results…further after cleaning place the coin in an air tight plastic bag so that there is no contact with air as air will make coin again dim…

Aarkay
Title: Re: Cleaning Silver coins with Brasso
Post by: Figleaf on October 11, 2012, 09:28:23 AM
Toothpaste also destroys patina and gives an unnatural shine. It takes much time to restore patina and in capsules, the patina will not be restored at all. There are better and safer ways to clean. They take more time, but collectors should know how to be patient.

Peter
Title: Re: Cleaning Silver coins with Brasso
Post by: FosseWay on October 11, 2012, 05:48:37 PM
Even on brass articles, Brasso should be used with caution. As said, it works by abrading the metal, removing the surface layer of oxide plus whatever stuck-on crud there might be. The abrasive nature of the polish is obvious if you use it on a coin (of whatever metal) because it wears down the design and there's something to compare the wear to. But if you polish something with a smooth surface, such as a motor car lamp or a trumpet, you are still removing the surface. Eventually you will wear through the metal.

When I was a lad I had a Saturday job at a mechanic's garage where old cars were restored. His speciality was pre-1920 cars, which used to have huge amounts of brass, plus lights and other accoutrements that were bolted onto the car rather than being integrated into its design as such elements tend to be on modern cars. These cars were already 80-odd years old and had been polished for that whole time. The guy I worked for was insistent that I (or anyone else) should only use Brasso on the lamps as a preliminary polish on lamps that had sat getting cruddy for years. For lamps that were already well cared for but were just a bit dirty, soap, water, clean dry towels and plenty of patience were the required tools.
Title: Re: Cleaning Silver coins with Brasso
Post by: Quant.Geek on October 11, 2012, 10:45:32 PM
I am so  scared of cleaning my coins that I don't even do it no matter how tempting it is.  I would rather send it to NGC for cleaning/grading as opposed to doing it myself, but I haven't done that yet.  I only have one or two coins I would even consider sending to NGC in my collection.  One being a 1840 Rupee like the one above and a Tiruvannamalai coin that has heavy patina which makes it really dark...


Ram
Title: Re: Cleaning Silver coins with Brasso
Post by: Abhay on October 12, 2012, 01:53:18 AM
Thanks a lot for all the replies.
Principally, even I don't clean my old silver coins, meant for my collection. But I do use Brasso often to clean common old silver British India Coins, which I had purchased about 7-8 years ago, in lots, at almost silver prices. Since most of these coins came from circulation, they are covered with dirt and grease. Since they are not very rare or costly coins, I clean them to find the different varieties among them,

Abhay
Title: Re: Cleaning Silver coins with Brasso
Post by: Ansari on October 12, 2012, 06:34:03 AM
I generally use Shock treatment  (learned from Peter) for coins i.e heating them up and suddenly dipping them in cold water.
Deposits like grease paint and other similar things are generally burnt during the process and can easily be brushed out.
Sand and other deposit also loose their grip due to sudden expansion n contraction.
Title: Re: Cleaning Silver coins with Brasso
Post by: FosseWay on October 12, 2012, 08:54:42 AM
Ansari, I'm intrigued. How hot do you have to heat them? Will boiling water do or does it have to be hotter and/or drier, e.g. in the oven? And doesn't the latter process make the coins change colour? The blade of my penknife has never been the same colour since I heated to sterilise it before performing an invasive procedure on my foot in the back of beyond. It's gone a not unattractive dark blue, but I'm not sure I'd want my coins to go that colour.
Title: Re: Cleaning Silver coins with Brasso
Post by: Ansari on October 12, 2012, 10:56:54 AM
Ansari, I'm intrigued. How hot do you have to heat them? Will boiling water do or does it have to be hotter and/or drier, e.g. in the oven? And doesn't the latter process make the coins change colour? The blade of my penknife has never been the same colour since I heated to sterilise it before performing an invasive procedure on my foot in the back of beyond. It's gone a not unattractive dark blue, but I'm not sure I'd want my coins to go that colour.

I heat them directly over gas flame till the deposits like greece, paint etc are burnt( Now thats the matter of experience).
Copper & silver won't change colour unless u overheat them. Even if they, can be turned back into original with the help of mild cleaning.

Blade is made up of steel i guess, so heating will change its colour.
Title: Re: Cleaning Silver coins with Brasso
Post by: dheer on October 13, 2012, 07:04:23 AM
Well if one is using the ordinary gas at home ... then ensure that the burners are clean and the color of flame is blue and not yellow ... yellow flame indicates impurities in the gas and can damage the coins ... blue flame is more pure ...
Title: Re: Cleaning Silver coins with Brasso
Post by: FosseWay on October 13, 2012, 10:06:43 AM
I have to say I'd never tried heating silver or copper over a gas flame, and had presumed it would have similar affects as it does on steel, as mentioned. But in any case here I don't have gas, so I can't try.
Title: Re: Cleaning Silver coins with Brasso
Post by: malj1 on October 13, 2012, 01:29:56 PM
I heat them directly over gas flame till the deposits like greece, paint etc are burnt( Now thats the matter of experience).

Grease and paint can easily be removed with paint remover, here this is obtainable in a small pressure pack container which helps considerably; wait five minutes then wash off in warm soapy water.

I would never, ever, use Brasso, a complete and definite no-no!  ::)
Title: Re: Cleaning Silver coins with Brasso
Post by: Figleaf on October 13, 2012, 02:08:23 PM
Malcolm is quite right. Paint can be removed by acetone (paint removers may contain other ingredients). Grease is best removed by soft soap, which will solve the grease and any acids.

While it is certainly possible to heat coins by an open flame, it is also risky. If you come too close, the metal may be discoloured. To avoid risk, you can use hot water to heat up the coin and iced water to cool it. Such treatment will indeed loosen layers of crud, so that the famous wooden toothpick can remove hardened dirt/grease and sand.

These methods should also work on BI rupees to dig out details hidden by dirt without damaging the coin. As a bonus, by practicing on the rupees, you acquire experience and confidence for cleaning more expensive coins without damaging them.

Peter
Title: Re: Cleaning Silver coins with Brasso
Post by: Coinsforever on October 13, 2012, 02:33:43 PM
I have never tried heating a coin to any temperature either by putting directly over flame or through induction heating. Sudden heating & sudden cooling convert  the metal into brittle and chances of damage is quite high . (Quenching (http://en.wikipedia.org/wiki/Quenching) ).

In industry normally all metals alloys after quenching /hardening goes for tempering (Tempering (http://www.tpub.com/steelworker1/11.htm) consists of heating the steel to a specific temperature (below its hardening temperature), holding it at that temperature for the required length of time, and then cooling it, usually instill air)

Paint remover , thinner or else are dangerous and deteriorate   the coin surface severely.

I prefer to keep the coins in original/natural  state , if rust appears on few of  the coins I quarantine such stuffs separately to avoid risk of getting contamination to other fine stuff.


Cheers ;D
Title: Re: Cleaning Silver coins with Brasso
Post by: asm on October 13, 2012, 02:55:25 PM
I have used various methods but never Silvo or Brasso. They require a lot of rubbing and leave the chemicals on the coin..........As regards heating, I have never tried it till now.

Amit
Title: Re: Cleaning Silver coins with Brasso
Post by: cmerc on October 18, 2012, 10:06:48 PM
I used brasso to clean coins when I started collecting 14 years ago.  The coins looked nice and shiny then.  Over time, a strange patina develops and the coin appears clearly cleaned.  Bad idea, damaged some nice coins this way-lots of visible hairline scratches.  NO BRASSO.

I also tried using vinegar (acetic acid) to remove tarnish from silver coins.  It does a decent job, most of the black patina seems to go away, but the coin loses its appeal.  There will always be black patches where the staining/toning is stubborn and they will look ugly.  Again, not a good idea.  NO VINEGAR. 

With my coins, i just rinse them in acetone for ~15-30 secs, or leave them soaked for a few mins at most.  It takes care of most of the oils on the coins.  If the coin is XF or below, and there is paint, green residue, etc., I wet the affected areas with acetone and lightly touch with my fingers to see if it comes off.  If not, I leave it alone and try to upgrade it with a better condition coin. 
Title: Re: Cleaning Silver coins with Brasso
Post by: bruce61813 on November 07, 2012, 02:57:36 AM
Brasso is a no-no, as in several of the threads, it is abrasive. For silver there are some high quality silver cleaners, that are not abrasive. they tend to leave the surface a bit dull. this can corrected by rubbing with a soft cotton cloth . The black silver oxide should also be removed. If it is grease/finger oils ordinary alcohol soak followed by a soft cloth rub should take it out. Heat is not good, as with the knife blade, at its annealing temperature, silver will blue and it goes through the metal and is permanent. 

On solid silver, 6 vdc low current electrolysis does work to remove thick oxide . But  [the big oh by the way] never do this with plated items, the thick black oxide is the surface silver, remove it and the surface silver is gone. There  are times when it is a choice, see the attached photo. This was a black lump of oxide, very little detail, so i went for some detail.

Bruce
Title: Re: Cleaning Silver coins with Brasso
Post by: Figleaf on November 07, 2012, 10:24:08 AM
Choice medal, Bruce. Glad it met you.

Peter
Title: Re: Cleaning Silver coins with Brasso
Post by: bruce61813 on November 07, 2012, 03:14:12 PM
So am I. But back to the point, as you can see, the sliver on the back has been stripped. When I received the medallion the back look blank, but i decided to remove some of the oxide, and the  back went from blank to readable. I removed the minimum to be able to read and see what was there. Call it a cautionary tale about preservation.

bruce
Title: Re: Cleaning Silver coins with Brasso
Post by: Figleaf on November 07, 2012, 04:16:08 PM
Since most of the damage was on one side, I suspect the medal was stored in an inappropriate way for many years.

Great job to restore its readability. Since the details are still loud and clear, I suppose it's just a case of a missing top layer that may have been applied after the medal was struck in the first place. If this medal would have been treated with an abrasive instead, more than the top layer would have been lost. It would have attacked the detail.

Peter
Title: Re: Cleaning Silver coins with Brasso
Post by: bruce61813 on March 31, 2013, 05:37:17 AM
I agree about the poor storage. I suspect that the black is silver sulphide mixed with some other silver oxide. So, I intend to leave it. The silver plate is mostly gone from the reverse. I could work on it, but best left as is.

Bruce