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Author Topic: A Question About Flow Lines  (Read 153 times)

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Offline Ken W2

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A Question About Flow Lines
« on: July 16, 2022, 03:34:40 pm »
We frequently see coins with obvious flow lines in tight spaces like within the letters of legends and between the legend and the edge, but which don't have flow lines between the legends and the bust or other main devices (of course we might see them under magnification).  The photo below is an example.  Does that occur because at the time of striking there is a lot of metal moving in a relatively small area, and as a result the die wears more quickly in that area ? Said another way, there is less space for the energy of the strike and metal movement to be diffused and thus the die wears more quick in the tight spaces ? 

Offline Kevin D

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Re: A Question About Flow Lines
« Reply #1 on: July 16, 2022, 05:46:22 pm »
I believe it does have to do with the metal movement of the flan or planchet when struck by the dies. The metal movement at the center of the flan or planchet is more toward the die cavities (design elements) than towards the outer edge (though there is some movement in that direction as well). The metal movement at the periphery of the flan/planchet is increased towards the outside edge. This is accentuated in ancient coins because they were not struck with a die collar, so there was nothing to restrict this movement of metal. This greater movement of flan/planchet metal at the periphery caused an increased level of die wear in this area.

The US mint used an 'open collar' until the 1830s, when they switched to a 'close collar'. Pronounced flow lines are often seen at the periphery of early US coins, the bust half being a good example. After the switch to the 'close collar', there was a great reduction in metal flow die deterioration at the periphery.

Offline Enodia

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Re: A Question About Flow Lines
« Reply #2 on: July 16, 2022, 06:30:41 pm »

Online maridvnvm

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Re: A Question About Flow Lines
« Reply #3 on: August 05, 2022, 06:08:33 am »
I owned a coin several year ago that comes to mind in this discussion. I sold it through Forvm and thus share their image:-



Both side show flow lines radiating from the bust and from Vesta not just on the legends....

Offline Joe Sermarini

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Re: A Question About Flow Lines
« Reply #4 on: August 05, 2022, 09:55:56 am »
Those flow lines attractively radiating from the center are much more common on denarii of Antoninus Pius than on those of other emperors. They must have used a blank flan that was considerably thicker in the center.  I believe these flow lines were intended, with aesthetic or anti-counterfeiting intent or both.
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