Starburst error

echidna · November 17, 2016, 08:46:50 PM

Have seen a number of these with a similar "starburst" effect.
Genuine or PMD ?

trout · November 17, 2016, 08:49:34 PM

I think that this has been affected with acid, how much does it weigh ??
A normal penny is 9.45g.

echidna · November 17, 2016, 09:09:19 PM

Dont actually have this coin yet so dont know the weight.
Its definately a thin planchet.

Noelos237 · November 17, 2016, 09:18:26 PM

Quote from: 'trout' pid='101576' dateline='1479377974'I think that this has been affected with acid, how much does it weigh ??
A normal penny is 9.45g.

I agree.

robbiegal · November 17, 2016, 10:41:29 PM

yes i have been told that they are acid
doesn't quite explain the long thin denticles to me

but i have definitely been told that by someone who actually put pennies into acid to prove it

Fulvio · November 18, 2016, 05:22:16 AM

Yup. Add this to the Shed Job file, under 'Acid Wash', just like your jeans.

Anytime you see a surface like that, its not original.

markn · November 18, 2016, 12:53:02 PM

Acid. The areas of metal that are deformed the most when the coin is struck are usually eroded the least. That's because the more deformed areas have a larger grain size and therefore less grain boundaries than the less deformed parts. Grain boundaries are the areas in metallic microstructure that are most susceptible to erosion by acid hence MORE deformed areas are eroded LESS than the less deformed areas.

That's why the denticles appear so long. When the coin was struck metal flowed radially outward to fill up the denticles on the dies and now that it's been treated with acid you can see where the metal flowed from.

Interestingly if you annealed a coin after it was struck and then treated it with acid it should (in theory) erode evenly all over. Would be fun experiment for someone with a small furnace and some acid.

echidna · November 18, 2016, 10:05:00 PM

Quote from: 'markn' pid='101596' dateline='1479435782'Acid. The areas of metal that are deformed the most when the coin is struck are usually eroded the least. That's because the more deformed areas have a larger grain size and therefore less grain boundaries than the less deformed parts. Grain boundaries are the areas in metallic microstructure that are most susceptible to erosion by acid hence MORE deformed areas are eroded LESS than the less deformed areas.

That's why the denticles appear so long. When the coin was struck metal flowed radially outward to fill up the denticles on the dies and now that it's been treated with acid you can see where the metal flowed from.

Interestingly if you annealed a coin after it was struck and then treated it with acid it should (in theory) erode evenly all over. Would be fun experiment for someone with a small furnace and some acid.

Thanks Mark