Letter 34058

What does Copper Have In It That It Kills Bacteria? [Indiana] 

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Hi,

I am doing a science project.My title is 'Can one penny make your roses last longer'? Supposedly the COPPER in the penny kills the bacteria in the water which the roses lay in. So my main question is what does copper have in it that it kills bacteria. Or what does copper have in it just in general? Please help me out on this one!

Faiza J.
student - Portage, IN, United States

Copper has only copper in it, Faiza. Copper is one of the about 102 'elements' that cannot be subdivided into something else. Some metals like copper and silver and cadmium are unnatural environments for some life forms and will kill them. Copper is used to kill plant roots in old pipes and to kill algae blooms in ponds and lakes. But that doesn't necessarily mean that putting a single penny in your rose water will actually do anything; you'll have to try it.

Ted Mooney, P.E.  finishing.com Brick, NJ

Copper salts are used by the wine growing industry to reduce the effects of fungus on the leaves and grapes. The mixture is called "Bordeaux Mix". I have not heard of copper being a bactericide, but it certainly does treat some fungal infections. As I understand it, the copper is toxic to the fungus and kills it off, like poisons such as strychnine or arsenic kill people and animals.

Take Ted's advice and do the experiment, but make sure you also use a control rose that doesn't get the copper treatment. Its Valentine's Day soon, so perhaps your favourite partner will buy you a bunch of roses to try out!

Trevor Crichton R&D practical scientist - UK

You might try looking at the copper nails or copper banding techniques to stop trees growing at how the copper sulphate plays a part.

Richard Graham
- Guisborough, UK

Hi Faisa,

Well,you sure got a lot of replies to your question. Good
replies, too.

Trevor's reply indicates a very intimate knowledge of the wine industry. Um! Lucky guy, eh?

Jim's assertion that animal dung is a good medicinal remedy which raises the point of human dung being perhaps even better, or ???

If you keep any fish, maybe you should not use copper piping as with hatchlings, ie. tiny fish, it was found
out that copper would cause them to die ... the answer being in using PVC.

Freeman Newton
- White Rock, B.C. Canada

I've never heard of using copper to kill bacteria, but silver is used quite commonly. There are many high-end antibacterials being made with tiny particles of silver. To top that, Band-Aid is making band-aids with woven silver instead of normal cloth band-aid material. It has something to do with silver interfering with the life-cycle of bacteria, preventing their reproduction. Note that it's actually solid elemental silver, not silver ions. Silver ions readily bind themselves to DNA molecules and other proteins and can actually poison humans. This is similar to the effect that copper salts (dissolved copper ions) have on fish, thus making them a good way to keep your pond blue and algae free, as well as a good way to poison fish.

Patrick R
- Student - KY, USA

Remember: Newer pennies are only 2.5 percent Copper!

David O'Neill
- Philadelphia, PA, US

E. coli O157:H7 has been associated with several large-scale food recalls by processors in the United States. This bacterium was found to be nonviable in a few hours when placed on copper surfaces, but survived for many days on stainless steel. The copper alloys tested included coppers, brasses, bronzes, copper-nickels and nickel silvers. The results confirm that the antibacterial effect is present in all the tested copper alloys, and increases with the copper content of the alloy. Furthermore, as expected, this action was faster at the higher temperature. The bacteria were found to be nonviable on almost all of the copper alloy surfaces in the range of one to six hours at 20°C. It took longer, with a minimum time of three hours, at 4°C. This anti-microbial attributes of copper alloys should be useful beyond food processing applications.

Chris
- Tempe, AZ, USA

American Pennies made prior to 1983 have little copper in them.
Silver is a much more powerful killer of bacteria.

Dave Block
- Peoria, AZ, USA

Thanks, Dave. Your second statement may be true, but your first one is ridiculous :-)

Coins before 1982 were 95 percent copper according to the U.S. Mint website.

Ted Mooney, P.E. 
finishing.com
Brick, NJ

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