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Solvents 101

 
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Bedrock of the Community
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 Posted 12/31/2008  12:27 am Show Profile   Bookmark this topic Add BadThad to your friends list Get a Link to this Message
I just want to try to explain a little about solvents. There seems to be lots of questions on CC about them.

I'm sure people will add to this or correct me.

The Rule: Like dissolves like.

Substances on the surface of a coin can vary greatly. We have to think of them in terms of polarity. What the heck is "polarity"? The term polarity:

http://en.wikipedia.org/wiki/Chemical_polarity

In a nutshell, think of the stuff stuck on the coin (goo) as having a negative or positive charge on one end. The stronger that charge, the more "polar" the goo is. If it's polar goo, you have to dissolve it into a polar solution. If it's non-polar (no charge at all on the goo), then you have to dissolve it in a non-polar solution.

Whew....are you with me here still? That's a lot of scientific mubojumbo!

When I work to conserve a coin, I'll use a range of solvents. The goal is to go though a polarity scale until I hit the right solvent. It's usually best to start with the more polar solvents first. Water is the best polar solvent in the world, mainly because it's normally completely safe.

OK, I'm outta gas here! Let's cut to the polarity chase! Here's what I use in order of polarity (at least with what you can get):

1) water (polar)
2) acetone
3) isopropanol
4) xylene (non-polar)

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 Posted 12/31/2008  12:35 am  Show Profile   Check TNG's eBay Listings Bookmark this reply Add TNG to your friends list Get a Link to this Reply
Alrighty then, what do you think of a chemical named Trichloriethane which I have a bottle of BLUE RIBBON distributed by Harco ( 10 or 15 years ago ) used as a soil and coating remover?
I also have a very old can of Trichloroethane ( slight spelling difference ) that seems to me to do about the same thing?
So how bout those big chemical words? Do you think there is a way to use these safely on a dirty coin?
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Edited by TNG
12/31/2008 12:37 am
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 Posted 12/31/2008  01:54 am  Show Profile   Check BH1964's eBay Listings Bookmark this reply Add BH1964 to your friends list Get a Link to this Reply

Quote:
I also have a very old can of Trichloroethane....


I use to work as an environmental rep for a bearing manufacturer and trichloroethane (methyl chloroform) was used for years as a solvent to clean bearings after grinding operations. This is not a solvent I would use without a respirator.

My former company paid millions of dollars in OSHA related medical claims to employees who inhaled the fumes when the ventilation systems were not functioning properly. Many are now disabled due to respiratory failure.

If I had a very old can of it around I would consider HazMat training!

As far as cleaning coins with it, let's stick to tried and true methods. This is NOT a substance to play with.
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Bedrock of the Community
United States
16207 Posts
 Posted 12/31/2008  02:30 am  Show Profile   Bookmark this reply Add BadThad to your friends list Get a Link to this Reply
Indeed, but it's an excellent solvent. I've never tried it on coins because it's a banned chemical. You better be real careful with it, read up on it:

http://en.wikipedia.org/wiki/Trichloroethylene

I think it would be far to harsh on coins, but it should definately strip them clean. I would dilute to a 5-10% solution it with ethanol before trying...if do you decide to try it after reading the above.
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 Posted 12/31/2008  03:56 am  Show Profile   Bookmark this reply Add T J to your friends list Get a Link to this Reply
BadThad,
great post.thanks for the information
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13235 Posts
 Posted 12/31/2008  04:01 am  Show Profile   Bookmark this reply Add Sap to your friends list Get a Link to this Reply
Trichloroethylene and trichloroethane are different chemicals. Both are chlorinated hydrocarbons, and I would avoid using either on coins, especially trichloroethylene - it's related to vinyl chloride, and like PVC it seems to me it could easily react to produce hydrochloric acid on metal surfaces.

They're also potent greenhouse gas compounds, and not good for the ozone layer, either.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
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 Posted 12/31/2008  08:01 am  Show Profile   Bookmark this reply Add tornandfrayed75 to your friends list Get a Link to this Reply
I thought it was a sin to clean and/or alter a coin.
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 Posted 12/31/2008  08:17 am  Show Profile   Check rggoodie's eBay Listings Bookmark this reply Add rggoodie to your friends list Get a Link to this Reply
You are correct but some collectors try to "conserve" a coin
no cleaning method is universally accepted among collectors.

And most would never buy a cleaned coin
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 Posted 12/31/2008  10:05 am  Show Profile   Bookmark this reply Add MorganNoob to your friends list Get a Link to this Reply

Quote:
I thought it was a sin to clean and/or alter a coin.


Washing a coin in water or acetone to remove foreign matter is hardly cleaning. IMHO, I don't care what is done to a coin as long as it doesn't alter the surface of the coin and it is completely undetectable when finished... But that statement is a very slippery slope, one day you are giving acetone baths, the next you are using steel wool.

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 Posted 12/31/2008  11:28 am  Show Profile   Bookmark this reply Add okie-colin to your friends list Get a Link to this Reply
My experience with acetone yesterday with old circulated Walkers, is that it removed that greasy, oily feel without removing anything else from the surface of the coin. The surface of the coin and patina was essentially unchanged, but they were brighter with the oily film removed. They do not look cleaned, ergo I do not consider them cleaned in the way we use that term in numismatics. I have used acetone on silver coins that had other problems, like heavy carbon spots or discoloration and it didn't help at all. Thanks for the great info BadThad!
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 Posted 12/31/2008  12:19 pm  Show Profile   Check TNG's eBay Listings Bookmark this reply Add TNG to your friends list Get a Link to this Reply
Leave it to Harco to put out yet another product that would be bad for coins. I did get to thinking ( and yes I had the caps on tight ) about Thad's "like dissolves like" and the company Harco and the green slime that some of the Harco books and holders caused on coin surfaces.
I thought maybe I had a solution ( pardon the pun ) to maybe removing some green or blackened slime on some coins.
I am glad to know that these are different chemicals. I might go out on the porch this summer and be upwind and try cleaning off some grimy common coins with both. If this does not work well, I might use it on some fishing reel gears instead. LOL!
Thanks guys and gals. I appreciate the input and advice.
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 Posted 12/31/2008  1:55 pm  Show Profile   Check BH1964's eBay Listings Bookmark this reply Add BH1964 to your friends list Get a Link to this Reply

Quote:
And most would never buy a cleaned coin


I beg to differ. While most of us would not buy a slabbed coin labeled "Cleaned" or "Improperly Cleaned", most of us have bought raw coins that have been cleaned.

I'd bet anyone who has purchased more than 5 raw coins has bought a cleaned coin.
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 Posted 12/31/2008  2:20 pm  Show Profile   Bookmark this reply Add jbuck to your friends list Get a Link to this Reply

Quote:
I'd bet anyone who has purchased more than 5 raw coins has bought a cleaned coin.
I have to agree; but acknowledge the possible exception for the most meticulous and extraordinary collector.
Bedrock of the Community
United States
16207 Posts
 Posted 12/31/2008  5:41 pm  Show Profile   Bookmark this reply Add BadThad to your friends list Get a Link to this Reply
There's a difference between cleaning and conservation. I consider what I occassionally do as conservation. The original surface is intact and there's usually no evidence surface debris has been removed. I've never conserved anything but copper, so that's where my experience speaks from.

It's a sad fact that copper is highly reactive and picks up gunk like a magnet to iron. Often, it's a choice whether to conserve the coin or live with one that's nearly worthless because it's so gunked-up. Here's a case in point, I'd personally rather have the coin after it's been properly conserved versus the top picture. I achived this using a range of solvent polarities and VERDI-GONE™:

Lincoln Cent Lover!
Edited by BadThad
12/31/2008 5:42 pm
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