I'm think primarily of silver here, but also of copper. So, is there evidence? If so, how would pre-striking toning be differentiated from post-striking toning? If a planchet were toned, perhaps the toning would be scraped from or stretched thin on the nearly vertical sides of some devices during striking. Cal
I'm neither a chemist nor a metallurgist, but I can't imagine that enough time would elapse for the metal to tone before the planchet is struck...
At times past, and maybe present, things could be rather haphazard at the mint. I can imagine a bin or bag of planchets sitting for months or years before striking. Plenty of time to acquire toning. Cal
I bet @dcarr has probably struck previously toned planchets before and can elaborate on the effect the strike has relative to the toning whenever he stops by
I think some toning is more than a few molecules thick. What do you think would happen to the toning if a toned planchet were struck? Flake-off? Mix-in with surface metal as it flows? I don't know. Cal
It's always been a point of intense curiosity for me, how metal propagates during the strike. I've urged Dan Carr to do some investigating, since he has a genuine Mint press, but it'd be a pretty involved process. It seems intuitive that very little of the exterior layer of the planchet would remain *exactly* where it originally was, even if it only moves in the Z axis. Specifically, I think individual spots of toning would probably "survive," but I kind of doubt it'd keep the same geographic configuration. I'm thinking a fair amount of planchet metal tends to flow outward towards the rim during strike, and the pattern of toning might_just turn into a rather pretty bullseye-looking thing.
I am eager to see this discussion. Off to grab some popcorn with plenty of butter and salt. Edit - and a beer.
I agree. Some toning absolutely is, on coins. But on a planchet ? Doubtful. I'm not saying it's impossible, just not very likely. And that's pretty much what is written and often repeated. But stop and think, and you should then ask yourself, how can possibly true ? Picture a coin, a Lincoln, a Morgan, a Jeff, most any coin for that matter. Where are the fields ? In the vast majority of cases the fields are anywhere but the center. And the fields are where the metal comes from that fills the devices. And the majority of the metal goes into the central devices. So as the metal flows, it flows inwards towards the central devices - not outwards towards the rims - because it must.
A little of both, I think, but I see your point. From a mass standpoint, most of the planchet of course ends up towards the center where the most z-axis detail is concentrated. All the same, one has to assume that the field-field thickness is rather less than that of the original planchet - the only way to have enough metal present for the raised devices. Then we have to factor the rim gutter/rim itself and the reeding which is by definition slightly larger i diameter than the original planchet (or it wouldn't feed). This is the place where the actual final thickness of the coin is the greatest, so it'll stack. Note I didn't characterize this as the "majority" of the metal flow. And keep in mind, with many issues (the Nickel you posted being one of them) the shoulder is the highest point or one of them) on that face, and it's at the periphery. That's why Lincolns tend to be weak at the shoulder and the O of ONE on the reverse; too much demand for metal there. Which is why I want so badly to see a metal propagation study. Much metal flows towards the center, but there's plenty of stuff heading towards the periphery as well.
Yes, a small amount of metal must flow outwards to fill the legends, from the portion of the fields closest to them. But some of the legend metal comes from the blank spaces between the letters and the protected areas of the letters. As for the rim, much of the metal for the rim is already there as a result of the upsetting. The upsetting is done for that very reason in fact because if it wasn't done the rim would never be filled. The metal for the reeds comes most from the blank spaces in between the reeds. Bottom line the vast majority of the metal flows inwards, not outwards. Yes of course, it's the exact opposite of a relief design. With relief the fields get thinner, with incuse the fields get thicker.
