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 Replies: 92 / Views: 16,260 |
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Pillar of the Community
United States
3499 Posts |
I am presently attempting to clean some ancients with 3% concentration hydrogen peroxide. I found on a few websites that this is a viable mode of dealing with encrusted dirt. But as I watch the coin in the liquid I can see tons of bubbles coming off of it. Just what is happening during this process? Are the bubbles indicative of a reaction between the liquid and the dirt? Also, just how long would this process take since my Hydrogen Peroxide is just 3% ? Thanks!
Edited by Archraz
10/01/2011 3:22 pm
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Moderator
 United States
23731 Posts |
At only 3% you might get some light cleaning effect of just the loose dirt. The effect only last a few minutes at best. Hydrogen peroxide starts to break down once it hit the air.
From what I've read about using hydrogen peroxide the solution is much more concentrated and very dangerous.
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Pillar of the Community
 United States
3499 Posts |
echizento- Thanks for the input. So I have a couple of ancients that have been in peroxide for about a day now, and the bubbling is still quite active. So this is not really doing anything?
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Moderator
United States
23731 Posts |
If it's still active it could be dissolving the calcium in the dirt. I would remove a coin and see if there is any difference. I think I'm going to try an experiment on one of my crusties and if it has any effect.
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Moderator
United States
23731 Posts |
I have a few crusties soaking in 3% for several hours now. The only results so far have been that the lid popped off forgot that I needed to vent it.
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Pillar of the Community
United States
3499 Posts |
echizento- hmmm, interesting, interesting.
Well, I have two Constantius II bronzes recovered from France in the peroxide. Both have been soaking for about a day. Once is still covered in bubbles and is giving off some fizz, but the other is REALLY active. In addition to give a very noticeable stream of fizz that quickly zooms to the top, it is surrounded by bubbles and every so often the coin slides around the bottom of the glass from bubbles attached the underside of the coin dislodging and floating to the top. And this is just from day-old 3%. So this is why I am wondering just what is going on in there.
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Pillar of the Community
United States
3499 Posts |
A bit of an update: I put a cleaned ancient into some peroxide in order to act as a control coin. And there are a few bubbles along the surface, but after about 3 hours almost no fizz is seen zipping up to the top of the glass. So it is obvious that the amount of fizz has to do with the dirt that is cemented. So any ideas exactly what is goin' on in this chemical reaction?
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Moderator
United States
23731 Posts |
I just checked the ones that I put in and they do seem to be cleaner. There is some bubbling but not a lot. I'm going to leave mine in over night and see what happens.
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Pillar of the Community
India
1995 Posts |
As far as I know, hydrogen peroxide bubbles out only nascent oxygen and the rest is merely water. This nascent oxygen is harmful to biological tissue in high concentration but metal is safe, I think. (unless there is oxidation at room temperature). Any chemist who would supplement?
Edited by drnsreedhar
10/02/2011 12:35 am
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Pillar of the Community
United States
3499 Posts |
Another update: So I just checked one of the coins which has been in the peroxide for a little over a day now. Interestingly the brownish cemented dirt and other material has started to change color. It now appears kind of grayish-whitish. So I took a Q-tip and rubbed the surface a bit on one side. And some of this whitish material did come off a bit. So I am starting to wonder if this is a slow but steady process of removing some of the layers of dirt. There still is a lot of dirt stuck on there, but it does look a bit better after just 30 hours of so in the peroxide.
Edited by Archraz
10/02/2011 3:20 pm
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Bedrock of the Community
United States
12437 Posts |
The "good stuff" is 30% H2O2 but it is rather dangerous for an amateur to use as it can cause severe burns to skin. I imagine that it would be fairly corrosive to coiunage metals as well.
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Pillar of the Community
United States
3499 Posts |
biokemist6- Thanks for the input! But just what do you think is occurring with the 3%? Is it harming the coin in any way? Are the bubbles indicative of a reaction taking place? (Surely they are since far fewer bubbles occur on a cleaned coin, and none are detectable when there is nothing in the peroxide). Do you think that doing this for a while may eventually lead to the breakdown of the dirt and other materials on the coins' surfaces?
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Moderator
United States
23731 Posts |
I just checked the ones I had soaking overnight and was surprised to see that the coins were much more cleaner.
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Bedrock of the Community
United States
12437 Posts |
Yes, the bubbles indicate that the H2O2 is reacting with surface contaminants. The bubbles are pure oxygen which are formed through the process of oxidation reacting with the mineral concretions on the coin. 3% should be adequate for what you are doing, a stronger solution could potentially react with the metal itself.
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Pillar of the Community
United States
3499 Posts |
biokemist6- Thank you very much for the input! That is great to know. It is very interesting that more than 3% could be harmful to the coin since so many websites I have read keep saying that one should use 20-40% concentrations.
So how long before Hydrogen Peroxide loses its potency? I mean I have some coins still bubbling after about 48 hours.
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Pillar of the Community
United Kingdom
2838 Posts |
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Replies: 92 / Views: 16,260 |
Posted 10/01/2011 4:47 pm
