What happens to a "woody" that is acid etched?

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Doug, I'll disagree with this: "Well except for one thing, maybe a couple of things. Like 1 - when strip is rolled, it's not little short, flat little strips that you can pick up and move around. It's in a big roll. And 2 - the roller presses only run in 1 direction. So the only way to run the strip through a 2nd, 3rd, ..... time is to move it around to the start point and do it again."

While turning the ingots into strip that is thin enough to punch out planchets, it is passed through the hot rollers back and forth. At each pass the rollers have been adjusted closer.

 

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It depends if they have the volume to continuously run the machines (which the mint's supplier most certainly does). If the machines are in use regardless, the cost of overheard is there in either scenario. Machines that aren't running aren't making money. Thus it's generally the downtime that will break a machine shop. Every time the material needs to be manually moved; it's not being processed: downtime. Every time somebody needs to make a minor adjustment: downtime. The downside of this system is if one cog in the wheel fails the entire operation is down; however, with these types of machines I doubt there are too many catastrophic failures due to the relative simplicity of the operation.

 

Not to just jump in, but when the strip comes from a roll, it would be difficult, if not impossible to re-orient.

I was not aware that the Mint flattens ingots to make planchets. I always thought that it came as a rolled strip. Am I wrong about that?

 

This is an age thing Mike...They don't do any of that anymore. Now the strip comes from outside vender in huge coils ready to go to blanking machine. For all I know, they get the blanks already made from the outside now! NOTE: DO NOT TAKE THAT AS GOSPEL as I stopped caring how coins were made after the 1980's. I'll need to check.

I cannot remember when the Mint stopped rolling ingots into strip in house. Probably in the 1970's as if I remember, I saw the mills - still hot - but not processing (rolling strip) at the time.

I still want to understand that too. I thought the streaks were caused because the "pour" was not homogeneous - an "Improper alloy mix." Any stretching from rolling would just elongate (pull) the different color metals out.

Furthermore think of the problem of picking up a hot, heavy five foot long lump of rolled metal an carrying it around to pass thru again. Later the same operation would need to be done to a hot twenty foot long strip. Later, the strip would be 100' long, etc.

 

Its the HOT Rollers I am considering. There must be an excellent reason that they are kept hot, and how hot in regards to the components melting points. Outside of this discussion, I would think that the heat was to maintain the homogeneity of the mix as it was moved through the reducing stages. So could the wood grain be effects from "cold" rollers, where the metal formed into distinct clumps. since coin metals that aren't purposely layered ( such as zincolns)are bound by "metallic bonds", they do not tend, to form aggregates "grains" unless they are not cooled properly. Those that have silver soldered know very well the granulation that can form if the heat cycle is not correct. Jim

 

Well, it's the Canadian mint and from ~2007, but there is a How It's Made on coins where this process can be viewed. It appears this is a two stage process done with a roughing mill; then a finishing mill. They show the roughing mill moving in a back and forth motion. Pertinent information begins ~1:00. I'd imagine the finishing mill may be a one-way operation due to the length of the sheet.

 

The metal has a higher ductility when the temp is increased. I believe cold rolling induces work hardening, so keeping the metal hot makes it easier to roll.

Your comment regarding cold regions causing the wood grained appearance is interesting. It wouldn't surprise me if grains subjected to different thermal histories would etch differently. Still not sure if the this would cause differences in toning seen on the woodies. I'm leaning towards improper alloying for these, but it is something to consider

 

desertgem, posted: "It's the HOT Rollers I am considering. There must be an excellent reason that they are kept hot, and how hot in regards to the components melting points." I guess they were kept warm to help squeeze the metal. "Outside of this discussion, I would think that the heat was to maintain the homogeneity of the mix as it was moved through the reducing stages." Once the coinage metal is mixed, poured, and cooled into ingots it can no longer move around to cause the streaks, it can crystalize as it cooled as seen on the Indian cent I posted. So could the wood grain be effects from "cold" rollers, where the metal formed into distinct clumps. since coin metals that aren't purposely layered (such as zincolns)are bound by "metallic bonds", they do not tend, to form aggregates "grains" unless they are not cooled properly. Those that have silver soldered know very well the granulation that can form if the heat cycle is not correct."
I don't believe so. Once cooled everything is set. Drawing out the strip can only elongate any stuff.

mynamespat, posted: "Well, it's the Canadian mint and from ~2007, but there is a How It's Made on coins where this process can be viewed. It appears this is a two stage process done with a roughing mill; then a finishing mill. They show the roughing mill moving in a back and forth motion. Pertinent information begins ~1:00. I'd imagine the finishing mill may be a one-way operation due to the length of the sheet." I believe you are correct about the finishing mill. Wonder if the Canadian Mint still operates in this fashion?

GDJMSP, posted: "For years now the mint has received round blanks. Can't recall for how many but seems like it's been quite a few." Nice to know.

"From what I've seen it was always done with a forklift. And once it started to elongate and get thing enough, it was rolled into a roll as it came out of the rollers. But that may have only been a video from 1 plant. Like I said, I grant there there are several ways it could be done."

Not enough room on the floor for a forklift when there were rolling mills at the Mint in Philly. When I was in Denver, they did not make anything but coins. Never been to West Point but some friends have. I'll ask. BTW, the entire mint floor has been changed at Philly. Still no room for a forklift. Probably only used to load ballistic bags.

"We're in agreement. The streaks of genuine woodies are caused by improper allow mix, and as the coin strip is made the different colored metal gets stretched and pulled in all directions, up, down, and sideways. All of that is a given.

The questions, the only ones we should be discussing here really are things you pointed out by posting pics of what you did. That being that acid eats away the alloy impurity (the thing that causes the dark streaks) faster than it does the copper. That is a given as well. And that's why the coin you showed pics of looks like it does. I've never seen pics of one where somebody did that by the way. But I certainly understand how and why it happened.

Next question, was the guy who did that, used the acid on that coin, a nutcase, or was he somebody like me trying to find out if the coin was a genuine woodie or not?" Probably a nutcase as the coin was XF/AU and a better date.

"Last question, is the coin I posted pics of a genuine woodie?" Not to me - dark lines too even.

 

How many woodies have there been since the Mint went to copper coated Zinc planchets? My guess is none. I thought that we were referring to woodies and all of them should come from the era prior to 1983, shouldn't they?

 

I cannot recall seeing any "wood" dated after the 1940's. I'm sure they exist for dates in the 50's when the Mint was still rolling strip in house. Strip from vendors was probably checked closely for quality.

 

These are metallic bonds, not covalent nor ionic, all of the electrons are in clouds , so there would be no elongations of bonded structures that would visible except on the level of the microscopes that can image actual atoms, and that is extremely difficult with metals. You can hammer, compress, etc. gold to a sheet thin enough for light to see through, but there will be no grains, elongated or not. Copper has less ductility and copper mix even less, but ONLY non metallic should form grains, not the coin metals (IMO). I will have to dig out Metallic bond resources when College reopens from SB.

 

My point was why would we even concern ourselves with current methods when the coins we're talking about are from the previous era?

 

Non metallic atoms can form bounds with the metal atoms, this is how you get copper sulfide, chlorides, etc forming on the surfaces. If they are in the melt mix originally, they can bond also, but as with the surface the bonding is not "metallic bonding" these would be visible ( with some high magnification devices ) as little island in the sea of metallic electrons or on the surface ( maybe the famous 'gold red spots'). Non-metallic bounding has very little ductility. Try to flatten copper-sulfide like metallic copper , gold , or silver.

We have all seen coins with fiber hair, or other non-metallic material pressed into the srface of a metallic coin, and it stays there, but it is not chemically bonded with the metal, Just held. In the 1500 the Japanese metal workers made copper-silver layered metal objects ( Mukume Gane) which were fused together by careful control of kiln temperature so that the surface of the layers bonded with the diffusion of each into the other. Coming back into jewelry today by the way, Contamination of the surface of the layers would destroy the objects ability to bond. Hope this rambling helps
https://en.wikipedia.org/wiki/Mokume-gane

 

IMHO, we are making something that is very simple to understand into a mystery for the ages.

Melt some vanilla ice crème in a baking dish. Pour some Hershey syrup on it and stir it until there are still obvious swirls of different sizes. Freeze it. That's the ingot.

While frozen cut out some long chunks and let it start to soften. Before it gets too soft, mash it with a large board. That is the thinner strip - still with the swirls of dark chocolate. Now, look at it. Some of the swirls are sharp and some have started to blend into the white an have lightened. Some are only on the surface or 1/8 inch deep and other streaks go all the way through to the other side (coins are found like this). That's the strip.

The streaks in hardened metal are set for our purposes. They don't move around anymore but during hot rolling they may stretch and change position in the strip.

Different metals used in cents react differently to acids. The depth of the etching on the OP coin depended on the resistance (hardness) of the metal, the strength of the chemical (acid?) and the time it remained on the coin's surface. It is that simple.

Ever notice that the swirl pattern on some woodies looks just like the swirl pattern made in the paint pan used to "marble" paper? Woodies are made by incomplete mixing of the metals. It is that simple.

They are vary rare after a certain date which is (?). This should be fairly easy to determine: "Post your oldest woody and your newest." From what I have seen, Large cents are rare, Indian cents are scarce, Lincoln cents - pre 40's are more common. After that rare again.

The Indian cent I posted with the crystals is a totally different animal. That's a cooling thing.

 

@Insider
I have a question 4 you now:
Did you ever think that bugs bunny was attractive when he put on a dress and played a girl bunny ????

 

I do know the character Bugs Bunny! Unfortunately (for what I missed), I was a child prodigy from three. I was home schooled with tutors - college courses at ten, watched over and sheltered. I never saw a cartoon, played with kids, had comics, a TV, a bicycle, etc. Everything was in the grown-up world. I never learnd any people skills! It was not until I was in my 40's that I tried to catch up to normal folks by reading comics, Mad, playing with trains, watching TV, going to movies, etc.

Thank goodness my language tutor kept me interested in Greek and Latin by using ancient coins. My Science tutor worked at the National Museum and we went there a lot. I got to meet the Clain Stefanelli's and see things in the numismatic dept. that were never on display. That's why I got interested in coins. By then, I had several numismatists as mentors.