trying to understand better the definitions of MINT FROST vs just plain old >>>

[MikeKing]

>>>LUSTER.

 

ok, I think most of us know about the metal flow lines created by the impact during the minting process, and how it is actually some wear in the die that induces this, and how this causes light to be reflected off the coin producing a cartwheel effect.

 

And if a die is polished, or before enough wear occurs such that flow lines are created, the surfaces would go more towards PROOF LIKE (or PROOF if so intended).

 

But how do you define MINT FROST? and what is the physics (in lay terms) of MINT FROST? And how would you describe what it takes for you to call a coin FROSTY?

[LucyBop]

I don't know daddy-o, but here is a Frosty Frankie, look closely at the devices, as the frost appears to be very small little crystals...

 

 

[Stanley]

Here is some luster fer you mike

Caution..Bright Moderns

[WoodenJefferson]

To me, Mint Frost can vary as much as the coins themselves. The frost or crystallization appearance of specified surface areas can be accomplished in several ways.

 

One man made way is to "pickle" the die using diluted acids to etch away selected areas of the contact surface. By unevenly removing a minute surface layer of hardened steel, it causes that area to hold the molten surface metal in suspension to solidify into a matrix. This matrix refracts light back to the observer in all directions there by giving the appearance of frost.

 

The other man made method I am aware of is to "bead blast" using high air pressure, nozzle fed, size graded glass or steel beads. The selected areas are literally control blasted in order to dimple the hardened area. Timing is critical with this method as well as with the acid, so just enough metal is moved to create the frost once the coin is struck. If you can imagine millions of tiny little .005 inch beads striking the surface at 100 mph, each one making their own little mark, it does not take long to raise the surface of even the hardest of metals.

 

The last method is just the way Mother Nature creates beauty in the realm that surrounds her.

 

The standards that the mint uses to create dies is very tight and very exacting, but no two dies are ever created as equals. The processes to create a striking die are kept as close to tolerances as possible but some dies just naturally out perform others, creating some pretty spectacular coins.

 

The actual pressing machine can also come into play in conjunction with these high performance dies. The more pounds instantly applied per square inch, the faster the surface metal reaches a flowing viscosity to fill the voids. This can be seen in the San Francisco minted Morgan silver dollars where the presses could out perform those of Philadelphia and Denver. Even the New Orleans mint would get the right combination at times to produce some spectacular Morgan’s.

 

We also often talk about EDS (Early Die States) and how the coins produced by these dies are some of the best struck specimens available. Well some of these EDS also create some of the frosty devices and lettering that we see on some coins. The pristine contact surfaces of these dies can hold the molten surface metal in place for that instant, to create that light refracting surface matrix.

 

These unintentional creations are nothing but wonderful anomalies that get into our hands for us to marvel and enjoy.

 

These are just a few ways Mint Frost can be brought out on to the surface of a coin, I'm sure there are others...I may not be right with the analysis of metallurgy or physics, but its something to chew on.

[rrantique]

Excellent example of process Woody

[gmarguli]

But how do you define MINT FROST? and what is the physics (in lay terms) of MINT FROST? And how would you describe what it takes for you to call a coin FROSTY?

 

To me, mint frost is more satiny luster while regular luster is more flashy and reflective.

[MarkFeld]

But how do you define MINT FROST? and what is the physics (in lay terms) of MINT FROST? And how would you describe what it takes for you to call a coin FROSTY?

 

To me, mint frost is more satiny luster while regular luster is more flashy and reflective.

I agree, though, as illustrated by the "frosty" cameo Franklin, I think of frost on a Proof coin differently than on a business strike.