Coins stripped to bare metal overnight in olive oil/WD-40 mixture

[Danny S. Jones]

I've got a table in my office that is covered with ice cube trays filled with coins soaking in olive oil. They've been there a long time, and I needed to move them somewhere else to use the table for work. With nowhere else to put them, I poured the olive oil out of the trays into an empty plastic Coke bottle. I was experimenting with WD-40, and had one tray of coins soaking in it, which I poured into the bottle with the olive oil. I went through the coins, drying them off individually, but they were still so encrusted I didn't bother with trying to clean any of them. Almost as an afterthought, I put about 35 coins into the bottle with the olive oil (and WD-40) and placed the bottle on a bookshelf.

The next morning, I went to check on them and noticed a light brown layer of dirt that had settled to the bottom of the bottle, and the oil had turned a very dark green. I knew something strange had happened so I emptied the bottle and took out the coins to find that all but the hardest encrustations had dissolved into a light brown layer of sediment and exposed patina was stripped, leaving bare metal.

Needless to say, I was very upset... even if they were just some LRB AE3s and AE4s.

What happened? A reaction between the WD-40 and olive oil? Something to do with the bottle itself? A mysterious, 1700 year old curse by the pagan celators opposed to the Christianization of Rome?  I'd post a picture, but I'm too ashamed.

[areich]

If you can take a picture, please post one anyway.

[Potator II]

I would probably change the title of your thread in :  Coins stripped to bare metal overnight in WD-40 !!??!!??!!

Potator

[areich]

Neither olive oil nor WD-40 by themselves will strip coins overnight
but maybe it was the combination or they were already rotten from BD.

[Danny S. Jones]

Even if there were no patina underneath, or it was rotten with BD as Andreas pointed out (which could be as there are spots that are surfacing on the cleaned coins) what could have happened that would speed up the process of softening the encrustations and dirt to make it turn to mush at the bottom of the bottle in one night?

These particular coins were very heavily encrusted ones. I had just taken the coins out, picking at a few to see if the encrustations had softened at all. They were as hard as ever. The next day, after the olive oil/WD-40 in the bottle treatment, most of the dirt/encrustations had been stripped off the coins. I didn't take photos of all the coins, but here's one of them that was covered in a thick crust, and then after was stripped overnight. The before picture was from about a month ago, but it was covered just about the same when I placed it in the bottle.

[moonmoth]

WD-40 is basically white spirit (= Stoddard Solvent in the USA) plus a light mineral oil. It will not touch genuine patina, and does not seem to touch encrustations, either.  It will dissolve some types of artificial patination and colouring. 

Combine this with olive oil, and what do you get?  Nothing obvious that could strip a coin.  I am trying this out right now ....

[Danny S. Jones]

A probably very important fact that I forgot to mention... the bottle was bloated as if it were about to burst, and when I opened the cap, a lot of gas escaped. (odorless and clear) I am leaning towards the theory that the stoddard solvent in the WD-40 may have released some type of chemical in the plastic of the bottle creating a reaction with the coins. I sincerely doubt that the olive oil had anything to do with it.

[Dino]

I am trying this out right now ....

Careful.  based on Goldenancient's last post, I'd keep the bottle uncapped and in a well-ventilated area if it's releasing a gas.

[simmurray]

One simple factor here is you do not know what the encrustation were made up of, could be carrying any chemical which may react with WD40 or Olive Oil or was needing the solvent to become active

[Danny S. Jones]

One simple factor here is you do not know what the encrustation were made up of, could be carrying any chemical which may react with WD40 or Olive Oil or was needing the solvent to become active

That's true, and an unknown variable that I hadn't considered. Though I wonder what would be in the soil that would react to the solution like that. WD-40's main ingredients, according to U.S. Material Safety Data Sheet information, are:

    * 50%: Stoddard solvent (i.e., mineral spirits -- primarily hexane, somewhat similar to kerosene)
    * 25%: Liquefied petroleum gas (as a propellant; carbon dioxide is now used instead to reduce WD-40's considerable flammability)
    * 15+%: Mineral oil (light lubricating oil)
    * 10-%: Inert ingredients
The German version of the mandatory EU safety sheet lists the following safety relevant ingredients:
    * 60-80%: Heavy Naphtha (petroleum product), hydrogen treated
    * 1-5%: Carbon dioxide

The can I am using was not purchased in the US, and presumably, there are different mixtures of ingredients in different countries. Since it does not say, I can't tell you what that difference might be.

[commodus]

Wow.
I am at once horrified and itching to try this myself on some hopeless crusties.
What sort of bottle was used, apart from it being plastic?

[Paul D3]

I agree with Commodus. I am onboard with the rest in avoiding ever exposing bare metal but, as a last resort, coins reduced to bare metal sound better than a coin covered with permanent concrete crust. Think of them as looking as the ancients saw them. Remember, when the coins were in circulation, most of them probably looked like the Lincoln cents in our pocket-shinny as a mirror. A merchant in an ancient market probably would have looked at you funny when you offered him a coin with the green patina we so love. The coin will retone in due time

[Danny S. Jones]

Wow.
I am at once horrified and itching to try this myself on some hopeless crusties.
What sort of bottle was used, apart from it being plastic?

A common 20oz coke bottle with the PET symbol on the label, therefore it was made of polyethylene terephthalate, which is a thermoplastic polymer resin with the chemical composition of (C10H8O4)n. Trying to remember how to crack these chemical equations from back when I taught chemistry, I think I may have found a theory that would give us the secret ingredient to WD-40 (it's been kept secret for years) and possibly solve what happened.

Polyethylene terephthalate (C10H8O4)n (i.e. the coke bottle) will react to ethylene glycol (C2H6O2) to produce bis-ß-hydroxyterephthalate which is synthesized by the transesterification reaction between ethylene glycol and dimethyl terephthalate with methanol (CH3OH) and hydrogen as a byproduct. If there was ethylene glycol present in the WD-40, or if the hexane in the white spirit (stoddard solvent) produced a similar reaction. with methane gas as a byproduct, that would explain the gas released from the bottle, and the rapid dissolution or the encrustations, as ethylene glycol, methanol and hexane are all solvents.  

If methanol was the byproduct of a chemical reaction here, mixed with the other weak acids and solvents present in the solution would have produced a corrosive effect, as methanol will attack copper and copper alloys. (bronze) What appears to be bronze disease has popped up all over the coins. This may be from the exposed bare metal surfaces, but more likely it stems from chemicals in the solution still attacking the metal.

To those of you thinking about trying this, I would urge you to not do it. It may work on dissolving the encrustations on coins. It may do nothing at all. Or it may be very dangerous to your health and start a chemical process that will destroy you coins.

[commodus]

I paid under $1 each for some of my several thousand (seriously) uncleaneds that languish in cigar boxes. I think risking the destruction of the patina of some LRBs is worth it in the name of science (and fun!). Even if the whole coin were lost I am sure the world will be none the less for the loss of one or two crusty Constantius II AE 3s. I'll do it in a well ventilated environment.

[Danny S. Jones]

I'd actually love to recreate the experiment to try to figure out exactly what happened, but I don't have several thousand coins to spare. I'm sure I could spare a few, but after what just happened, I don't wanna.  If you're up for it, try a bottle with just WD-40 with the cap on tight to keep in the gas, and a bottle of WD-40 with the cap off. Then do a third bottle with a mixture of WD-40 and olive oil mixture. I would estimate that about 20-25% of the solution was WD-40. As a control you could have a 4th bottle with just olive oil. Be sure to take the bottles outside when you open the caps. Also make sure the bottles have a PET recycling symbol on the label.

Let me know how it turns out.

[commodus]

Will do!
Don't be jealous about the quantity of coins I cited. Almost all LRBs bought in quantity through the past decade or so, some literally fused together by their encrustations, though most I have separated by soaking for months in olive oil. I cherry pick the best items, use identifiable duplicates for trade material, and throw the rest in boxes for "some day." They are not exciting coins, trust me (unless you REALLY like low grade bronzes of Arcadius, Honorius, and the Constantine boys).

[Jan]

One suggestion could be that an electrochemical process took place if coins of different metal composition where placed togehter in the container. That could result in gas production just as in ordinary zapping of coins.

I hope I got it right that several coins where placed together...

Cheers,
Jan

[Danny S. Jones]

Will do!
Don't be jealous about the quantity of coins I cited. Almost all LRBs bought in quantity through the past decade or so, some literally fused together by their encrustations, though most I have separated by soaking for months in olive oil. I cherry pick the best items, use identifiable duplicates for trade material, and throw the rest in boxes for "some day." They are not exciting coins, trust me (unless you REALLY like low grade bronzes of Arcadius, Honorius, and the Constantine boys).

LRBs have never been my cup of tea, but lately I find myself spending hundreds of dollars on uncleaned lots. None of them seem extremely fascinating, but finding a nice coin, no matter what it is, under all that dirt is exciting. Although, I'm collecting more and more piles of "someday" coins too.

This little incident has given me the urge to try some new tactics, though stripped coins aren't really what I'm looking for either.

[Danny S. Jones]

One suggestion could be that an electrochemical process took place if coins of different metal composition where placed togehter in the container. That could result in gas production just as in ordinary zapping of coins.

I hope I got it right that several coins where placed together...

Cheers,
Jan

There were 35 coins in the bottle, but they were all late Roman bronze, presumably of the same metallic composition. I'm not sure if that's the answer, but I'm still not completely sold on the reaction between the WD-40 and the bottle either. Something happened, and I sure would like to know what it was. Maybe Commodus' experiment will shed some light.