Do flow lines appear on fake silver coins?

[Brian L]

I think I read somewhere,
one way to tell a real silver coin like a denarius  from a fake is flow lines.
Flow lines can't be copied,is this true?

[Akropolis]

Flow lines can't be copied,is this true?

As a general statement, false.
PeteB

[Brian L]

"As a general statement, false", Ok.
Let me put it another way,
If a coin has flow lines,it is less likely ,to be fake  or
realistic flow lines are difficult to counterfeit,
so it is not worth it for a common coin.
I am thinking in regrades to ebay denarii.

[PeterD]

A cast fake is usually (I'm generalising here) made by pressing a genuine coin into clay or sand to make a mold. In theory all details including flow lines will be transferred over. However, some details are lost on a cast coin, so if the flow lines are negligible they may be lost.

But in any case, by no means all silver coins have flow lines, so that's really no guide.

[Tiathena]

*
 
    It has long been my impression and understanding that – “..realistic flow lines are difficult to counterfeit…” is true.  Excepting those counterfeits which are actually struck.
 
  As Brian asks with particular regard to the more ‘garden variety’ denarii, too, it would seem to me a fairly decent signifier of probable authenticity.
  Probable – not a guarantee.
  ( The question doesn’t concern or apply to coins where no flow-lines are visibly present ).
 
  Do the experts in counterfeits disagree..?
 
*
 

[vitellivs]

to summarize:

 - fake coins could have flow lines
 - genuine coins could have flow lines
 - coins without flow lines could be genuine and could be fake

[Tiathena]

*
 
   To reiterate …
 
  The question is realistic flow lines on a Cast coin ..?
  Which may be that PeterD has already answered, but the brevity of his reply and its phrasing leaves the question still standing in my view.
 
  Even If a cast picks up and transfers flow lines, even If they are somewhat diminished in the process, to the extent they are at all visible, can, will, do they have a realistic quality and appearance? – or is that realistic quality typically sacrificed in the process?
 
 
  Best,
  Tia
 
*
 

[vitellivs]

 flow lines on cast fake coin are of "lower quality", the finest of them could be lost (or parts of them), or visual appearance is bad... but if we talk about appearance of flow lines on cast fakes... yes, that lines could be on fake coin, and these lines could be relative realistic...
 (relative = quality of process, quality of host coin, experience of person, microscope or just eye... etc)

[Sri_Sahi]

When we are talking about flow lines being captured in a cast, we are talking about the microscopic flow lines which give an uncirculated coin it's luster or frost, not the heavy flow lines which sometimes radiate outward very visibly from the letters and/or other devices. Heavy flow lines can be captured by even a simple sand cast. The microscopic flow lines, however, are much more difficult to capture. Even minimal wear erases flow lines completely, so for counterfeit detection, this test applies only for "mint state" coins. With today's high-tech pressure casting, I suspect even the finest details, including microscopic flow lines, can be reproduced on cast fakes but I'm not certain. Perhaps Dr. Propokov will weigh in on this thread.

[Will Hooton]

With today's high-tech pressure casting, I suspect even the finest details, including microscopic flow lines, can be reproduced on cast fakes but I'm not certain.

You are correct.

There is an anecdote from Charles M. Larson's Numismatic Forgery about a jeweler who cast a rose in Gold. After the golden rose was removed from the investment plaster, the cast, upon closer inspection, revealed a perfectly preserved aphid on the stem, cast in gold! Under a microscope, cast parasites were observed upon the aphids legs!

You might dismiss this as fanciful stuff, but blast/HP/microcasting is a real engineering process capable of reproducing such minute features.

[Joe Sermarini]

Flow lines are useful in authentication. 

A genuine coin struck from very sharp fresh dies will not have flow lines because the lines are actually the result of wear in the die from the flow of metal.  Flowing metal wears channels in the dies. 

Some types usually have strong flow lines.  Some types rarely have visible flow lines.  For example some Antoninus Pius denarii types almost always have very strong flow lines.  The fields almost seem to have a radiate pattern from the center.  Perhaps the planchets for these denarii are nearly globular prior to striking.  In this particular case it even seems possible the rays (flow lines) might be engraved in the die fields (but I don't think they actually are).   

To most effectively use flow lines for authentication, you should know what to expect for the type and the level of die wear. 

Pressed fakes do not have flow lines.  This is quite often the biggest sign of a pressed fake.   

Cast fakes often do not have flow lines or the flow lines will be weaker than expected.   

[Sri_Sahi]

While I hesitate to disagee with our Forvm owner, especially while he is on vacation, I believe I need to reiterate and clarify my earlier post. The problem here seems to be one of semantics. All struck coins in mint state show flow lines. They are the result of the surface of the planchet liquefying under pressure during the strike and then re-solidifying.  It realy has little to do with the die itself. It is the light reflecting off this pattern of microscopic ridges - like waves on the ocean or frost on a window pane - which gives an uncirculated coin it's characteristic luster. These microscopic flow lines usually require a 10x or greater glass to discern. They can be very useful in counterfeit detection since they are difficult to capture in a mold. While flow lines are not individually visible to the unaided eye, the result on a freshly cast copy of a mint state host is often a "soapy" appearance, since the flow lines which gave the host coin it's luster are absent on the cast copy. However, high-tech modern fakes can and do fool even the most knowledgeable watchdogs including grading services and auction houses. This is why an absolute guarantee such as Forvm gives is essential.

When the flow of metal begins to erode the die and creates easily visible radiating lines, as Joe referenced, this is a form of "die wear" which should not be confused with "flow lines" in the strict sense.

For collectors of modern coins, flow lines are essential to proper coin grading. If a coin shows breaks in the pattern of flow lines on the highest points of the design, the coin can not be Mint State (60+) and can grade no higher than About Uncirculated 58 on the 70-point Sheldon scale. Unscrupulous dealers often pass these coins off as "Unc". In the industry they are known as "sliders" (not to be confused with the tasty little burgers at White Castle).

[Joe Sermarini]

When the flow of metal begins to erode the die and creates easily visible radiating lines, as Joe referenced, this is a form of "die wear" which should not be confused with "flow lines" in the strict sense.

No.  What you call "flow lines," is called "mint luster."  The forces that create mint luster are the same forces that wear the dies and create flow lines.  They are in some sense the same thing but also quite different.  You can describe mint luster as flow lines but mint luster is a specific type of flow lines and is best described as "mint luster."  You could describe the die wear effect created by metal flow as "die wear" but this specific type of die wear effect is described more accurately by "flow lines."

[Ryan C]

Thank you Joe for the clarification, I was starting to wonder if those markings(particularly on my Antonius Pius  denarii) were not actually flow lines according to the gentleman whose post appears before yours. I rely on experts like yourself and Dr. Propokov to explain the "lingo" and to give novices like myself a better understanding of ancient coin collecting in all ways.
Thanks again, Ryan