Patina; Natural vs Applied

[barriergeocon1]

I collect Civil War edged weapons. There are many modern reproductions that are aged to look like original period items. The components can include brass, iron, steel and leather). Unfortunately, many aged items are sold as original Civil War period items but are fakes.

Focusing on the steel components first, how can I distinguish patina produced by oxidation over a long period from patina reproduced by modern chemical aging? (Could one clue have something to do with the depth/thickness of the oxidized film?)

Thanks!

 

[Ron]

Artificial ageing is usually more consistent in its appearance than natural ageing. Also, you are more likely to see pitting corrosion in naturally aged parts.

Look for patterns that show that the part was maybe lying against something and there's a stain related to that. That's usually natural as opposed to artificially aged.

 

[barriergeocon1]

Ron, I appreciate your reply and have seen what you have described. However, I would ask you consider that original Civil War period Confederate weapons can range in price from just over $1000 to $500,000 and, as an example, a faker can commonly increase the price from $100 for a reproduction to $6,000 as an original period item...so these scoundrels that fake weapons are masters at what they do, as skillful as art counterfiters...because there is some real money in it.

To the observer, on masterfully faked weapons, the patina, pitting and wear appear authentic, so perfect even experts are often fooled. When I began collecting, I bought fakes thinking they were original and lost thousands of bucks...which is seen amongst collectors as paying your dues.

I have surmised that there may be a metalurgical method available to help protect buyers from this kind of fraud.

 

[Ron]

Artificial ageing is done with either acids or caustic solutions. The simple test would be a pH test on the surface of the obvious aged sections. Natural ageing would likely be near neutral in pH. Almost anything metallurgical will be destructive in nature and would damage the piece. You could do a microhardness test to characterize the metal, but that might be difficult to compare as well.

 

[Robertmet]

Discovering a fake requires examining a large number of items completely to look at the whole item in every detail.I think as far as scientific tests the best might be chemical analysis of the surface , again comparing it to known good samples.The more knowledge and experience you have the easier it will be to spot a fake.

 

[kclim]

See:

Scientific Investigation of Copies, Fakes and Forgeries By Paul Craddock

Fake patinas: their examination and production - pg 365

http://books.google.com.au/books?id...LvmZoB&sa=X&oi=book_result&ct=result&resnum=3

Makes mention of using XRD and examining underlying metal

 

[EdStainless]

XRD is a good tool. The most common issues that I have seen were related to alloys (modern ones do not match historic ones) and production methods.
Older alloy tended to have high impurity levels by todays standards. There are even some of these chemistries that have been documented.
In some cases where items could be slightly disassembled you could use a low power microscope to reveal tooling or machining marks that were clearly modern.

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Plymouth Tube

 

[barriergeocon1]

These are great suggestions...Thanks!