I soaked a copper cent in mineral oil for a month. Dirt on the coin loosed up and came off. Now, how do I remove the mineral oil from the surface of the coin? acetone? xylene? (Also, is it bad to leave a coin soaking in mineral oil for an extended period of time? 1 year?) Any help would be appreciated. Thanks, Doug Read more: http://www.cointalk.com/private.php?do=showpm&pmid=405884#ixzz1eSTOAhfX
Letting oil of any kind come into contact with a coin at all is a bad idea. And it's a bad idea precisely because of the predicament you find yourself in now. And before you ask - then how are you supposed to clean your dirty coins ? You're not supposed to.
Olive oil is best for soaking dirt off coins but should not be used on uncs or proofs. Mineral oil is OK but a second choice. I have very poor luck getting the oil off and the longer it soaks the harder. I find the best way is dish detergent but be sure to get it well rinsed afterward. It might take multiple attempts. I can't tell that leaving a tiny amount on does any damage but don't have a lot of experience yet. Everyone should understand to never clean a coin until they know how. Learn on junk coins and pocket change. It is far easier to destroy a coin with cleaning than to help it. The main thing you need to learn is how to identify coins that will be helped by cleaning rather than hurt.
Olive oil works only on copper and bronze (tin)(maybe aluminum). It only helps to remove encrustations. I use a locust thorn or tooth pick to gently pry things off to minimize soak times. You never really know what's under the encrustration and it could be a very serious flaw such as a hole or corrosion. But you can develop an eye that will give you abn idea. Often the coin is so ugly that you might as well try it. Sometimes a really beautiful coin is hidden under it and sometimes a dog. Don't clean nice collectable coins without any experience. Valuable coins should be sent in for professional cleaning even if you know how probably. Very old coins are almost always cleaned or they need it. I figure many coins look a lot better after you thumb a little oil into them so a small amount of olive oil that has penetrated the metal might not hurt.
Soaking in alcohol works just fine for removing any oil. If you can, try to get 192 proof (96%) neutral spirits. This stuff will do the trick pretty quick. Many liquor stores have that. If not, regular rubbing alcohol should do the trick, but may require a longer soak. Also, you won't get the discoloring affect that acetone can cause on some coins.
Oh well, I should know better than jump into such, but 1. Any oil other than some special synthetics ( clock oil) could have sulfur compounds, acid producing organics ( over time), that can damage patina and alter the surfaces. I wouldn't use oils, even though I do have clock oils for another purpose. 2. Acetone shouldn't have to be used beyond a few minutes in each of 3 soaks/rinse. The first should be the longest in case the oil has partially solidified. The oil can get into the "pores/pits of the surface and the acetone can only remove what it contacts. I would not use water or other solution such MS70, coincare, etc. after the acetone as why would you want water to get to the newly exposed surface. Hold the coin at an angle and rinse for a final time with acetone. Hold in fingers until air dry ( few seconds) and store. 3. Walmart sells 91% isopropyl alcohol in the pharmacy area, but that is still 9% water, so you still need an acetone rinse. 4. Ancients ( cleaning) has a long history, and different expectations by the collectors as moderns. Many people have issues with acetone, and that is a different opinion, and as usual, to each their own
Why not ? Because there are a thousand other topics and questions just like it and asked just as often. And if we made all of them a "sticky" then we would all have to scroll through numerous pages of stickies (which everybody would hate). Which would make none of them any easier to find than they are now without them being a sticky.
One small chemistry point: 91% isopropyl alcohol with 9% water is an azeotrope, a mixture that boils at a constant point. When it evaporates, it evaporates in that exact proportion -- it doesn't leave water behind. (This assumes, of course, that you started with a dry coin.) I don't know much about the characteristics of an acetone-isopropanol-water mix. It's conceivable (although unlikely) that you'd leave more water on the coin that way. BadThad?
Pure acetone is a better choice. Isopropyl alcohol will leave some contaminants on the coin after evaporation, in my experience.
How many of you have actually mixed mineral oil and acetone to see what happens? Acetone is a POOR choice for the removal of oils. Time and time again I see people say to use acetone and that is plain WRONG. Acetone is a very polar organic solvent and oil is completely non-polar. In chemistry there's a property we go by that's very simple: LIKE DISSOLVES LIKE. I suggest all of the people that recommend using acetone to remove oil do a simple experiment: Mix equal parts of acetone and oil in a glass container, mix well and let it stand for awhile. You will get two distinct layers. This clearly shows that acetone is the worst choice you can make when dealing with oil on a coin. The best (consumer) choice for removing oil is XYLENE. It is a non-polar solvent that is completely miscible with oil. To the OP: Soak your coin in xylene for a couple of hours, remove, and rinse with fresh xylene. Like acetone, the xylene will evaporate but it takes a little longer. If you want, you can rinse with acetone to speed the process.
Cladking....ya know I like you, but I have to disagree about using olive oil (actually, any oil), but OO is bad stuff for coins. It contains all kinds of impurites and the organic acids are corrosive to all metal surfaces. I've seen some pretty good conservation results but I'd argue there's far more bad results out there that we never hear about. I've done my share of experimentation with OO and I've seen some nasty, permanent damage to copper. My advice to collectors: DO NOT USE OILS ON YOUR COINS. I don't care what kind of oil it is, it has no place in the coin world IMO. This includes Coin Care which is 99.99% napthenic oil and odorant. The ONLY reason it's been used is that were few other choices. It's been used for decades (perhaps longer) and collectors have propagated the myth of how great it is for coins, that doesn't mean it's right. Sure, oiled coins look nice and shinny and great...until that oil is removed and the REAL coin is exposed. Oil is BAD STUFF!
I agree. There is a strong tradition of using olive oil in cleaning ancients. I believe this started before movern chemistry. Oo is a very light acid, meaning it will not damage a coins surface quickly, but has an acid to slowly help dislodge adhered particals and frankly the oiliness gets in between layers and helps dislodge them. However, oo will darken a copper coin in almost every case, and because its not a pure product can have varying levels of acids, making control difficult. My preference in cleaning coins is distilled water. Its water so no oil or acids are attacking your coin, but the lack of minerals in the water allows the water to dissolve the mineral on the coin. Always use large quantities, and change often. What you are doing is slowly dissolving the minerals on the coin in a completely safe environment, but the water will reach saturation point quickly so frequent water changes speed it up. Dislodge encrustations frequently, and put the coin back in fresh water to remove minerals from the freshly exposed surfaces. Not the fastest way, certainly not faster than an acid, but completely safe, and free if you simply use water from dehumidifier or air conditioners. The main caveat is to thoroughly dry when done and the coins will not longer be submerged in water, as water can promote bronze disease. Also, NEVER clean a coin with bronze disease with any other coin, or allow the water that the bronze disease was soaking in to contact another coin. After leaving US coins the only thing I have ever used for conservation has been pure water and renwax, a reversible coating.
I have never done it with mineral oil, but I have removed Blue Ribbon from large cents with acetone. It is my understanding BR is an oil, and it removed it quite well. I'll try xylene the next time, but have to pick some up.
There are many thousands of early copper collectors who disagree with your assessment of oil -- it has, and continues to be, widely used in that specialized area of coin collecting for its protective properties. That said, personally, I agree with you and do not use it on my copper -- to the contrary, I typically remove it....with acetone.
Quite correct. But not a one of those coins would be slabbed by NGC or PCGS. And before you say it, yes I know that in the past they have been. But today oils of any kind, waxes, Coin Care, Blue Ribbon - all of these things are considered contaminants by the TPGs. And saying oils have protective qualities is akin to saying that lacquer, shellac, varnish, even lucite, have protective qualities. Sure they'll protect the coins if you coat them with it. But what do you have once do ?
