A thread about what can cause coins to change/tone in their holders ....

[MarkFeld]

It is well known by most collectors that for various reasons, coins often change/tone to varying degrees in their holders. For purposes of this discussion, by "holders" I am speaking of third party grading company holders, as opposed to other types.

 

I was thinking it might be of some benefit to have a thread which contains the different causes of coins' changing/toning in their holders, and I am asking for your contributions (numismatic, not monetary ).

 

To get things going, I will list one cause - coins which have been dipped and improperly rinsed afterwards. Such coins usually develop staining/splotches/streaks as a result, later, if not sooner. By the way, it is my understanding that when a coin is dipped, the removal of the protective patina, alone, can make it more susceptible to reaction to the environment.

 

Who's next?

[bsshog40]

I don't really know Mark unless the insert could do it over time, sitting in a windowsill under the blazing sun, wrapped in a tacobell napkin with a pile of sulfur lying next to it.

[gmarguli]

Yeah Mark, like I'm going to give my secret techniques away! OK, here are some possibilities.

 

Slabs (which are not air/water proof) can be submerged in liquids which are reactive to metal.

 

They can be put in a chamber with certain gases. I suspect high pressure chambers would speed this up. Still, they can be put near reactive chemicals and change will occur.

 

They can be put in humid/hot environments.

 

Earlier inserts are known to have a reaction with coins.

 

Since slabs are not air proof, the toning process that was already started can continue.

[bsshog40]

I don't really know Mark unless the insert could do it over time, sitting in a windowsill under the blazing sun, wrapped in a tacobell napkin with a pile of sulfur lying next to it.

 

 

Hey Mark, I know this is probably a serious thread for you and was just making fun because I really don't know what would cause this. Did'nt mean to take the seriousness away.

[rrantique]

Mark I think the removal of the "protective patina or the lack there of" is the number 1 cause. Environment where they are stored and of course reaction of purity of the coin to different chemicals or gases. And Please don't forget those dirty fingers.

[WoodenJefferson]

Substitute a small amount of sulfur for water.

 

Sulfur

Melting point 388.36 K

(115.21 °C, 239.38 °F)

 

Polycarbonate (plastic)

Melting temperature 267°C*

 

 

Under ordinary circumstances (at standard pressure), liquid water cannot be heated above 100 °C in an open vessel. Further heating results in boiling, but does not raise the temperature of the liquid water. However, when water is heated in a sealed vessel such as an autoclave, it is possible to heat liquid water to a much higher temperature. As the container is heated the pressure rises due to the constant volume of the container (see the ideal gas law). The boiling point of the water is raised because the amount of energy needed to form steam against the higher pressure is increased. This works well on solid objects; when autoclaving hollow objects, however, (hypodermic needles, tools, etc.), it is important to ensure that all of the trapped air inside the hollow compartments is vacuumed out.

 

Simple autoclaves use a single pulse pre-vacuum, while a modern day autoclave has fractioned pre-vacuum that pulls the air out in several stages to achieve 100% steam penetration in the sterilization process.

 

Coin holders that are not sonically sealed or are not 100% air tight are the most susceptible, but a pin hole along the seam is all that is required to complete the transfer of clean air to one impregnated with a known toning agent. The key here is a vacuum and when the temperatures are brought down, the permeated sulfur laden pressurized air within the autoclave is drawn back into the coin slab.

 

Trial and error will allow you to adjust the autoclave temperature where the sulfur turns into a gas yet the high temperature attained will not melt the plastic coin slab. Setting the plastic on a heat resistant material such as ceramic will also help form pre-mature melt down.

 

Course, this is all "hypothetical"

[ldhair]

Changes in storage and environment can be a problem.

 

A coin can change because of the process of being sent in for grading. It gets removed from one holder and put in a new flip, travels by plane and trucks with all kinds of changes in temperature and humidity. Next it gets put in a slab and travels again. Just my first thoughts

[BankNote1]

Stuff left on the coin from the minting process. Junk breathed on the coin by the grader, grader's, and the dealer who owned the coin before it was slabbed.

[just-john]

I'm doing an experiment now leaving a slabed coin on my dash board for the summer here in Arizona.Todays temp was 108 f inside land cruiser had to be 180+ with windows up.Will

see how it looks in Sept.

[MarkFeld]

I'll add another one - coins which have been altered by the application of substances such as putty or, in the case of Proof coins (or business strike Morgan Dollars) artificial frosting. Often times, the substance, which was initially undetectable, later becomes (painfully) obvious/conspicuous.

[supertooth]

This may not be an exact answer to the question---but,IMO, needs to be said. That is that whether the coin is 'raw' or in a slab---if it is altered in any way---the coin is then usually immediately sold [i would think]. Then, its new owner places the coin in some sort of album or just into a slab box. It is then not usually viewed every day. After maybe months or years, the coin has then reacted to its current environment. Or has been allowed to have time to react to having been worked on. It is then that the consequences of the coin's coin doctor job becomes apparent.

 

Changing the coin's surfaces---as by dipping or some cleaning methods----seemingly makes those surfaces more receptive to the future environmental conditions that then present themselves. JMHO naturally. Bob [supertooth]

[pendragon1998]

I suspect that at least some spotting on coins is due to liquid microdroplets being sprayed out from compressed air blowing systems used to clear dust off of coins and holders before sealing the coin in. I don't know if that sort of blowing system is used at TPGs, although I suspect it would have to be or we'd find much more lint in our holders. I have actually seen the mint using compressed air on coins on television.

[DC Dawg]

What about the American Silver Eagles when they develop milk spots while slabbed? These are not dipped and rinsed, they are just rinsed by the Mint.

 

Scott

[Count_Erfit]

Reversion of conservation.

 

From personal experience.

[leeg]

This is one you don't see very often. When I got this coin in-hand I noticed it had a pin hole in the slab at the bottom of the mainsail area which caused the area under the pinhole to tone:

 

 

 

 

 

 

 

It's not attractive in my opinion and will go back to PCGS under their Grade Guarantee.

[leeg]

Heres another pinhole on the coin, not the slab, that had toned:

 

 

 

 

 

 

[pendragon1998]

So the question is: is that an actual "mechanical error" (i.e., a defective slab) or was it purposely done to AT the coin in-holder?

[Shortgapbob-migration]

Great thread Mark!

 

Sometimes on copper, if a small spot of verdigris is not neutralized before going into a holder, and the TPG holders it (which they do sometimes), the spot will continue to grow on the coin and become more of an issue.

[WoodenJefferson]

Coin Link Web page has NGC chat link

 

Link-a-fied

 

Go all the way to the bottom of the web page, look for a small block that sez:

 

FORUM WATCH

 

This thread is a clickable high light...very interesting, I did not know this information was so readily available to the coin world as such.

 

I may be a bit more careful what I say.

 

edit: opening statement

[bsshog40]

I posted this in my topic "NGC slabs are hermetically sealed". It would also work here.

 

So I would presume this would be the method for sonic sealing slabs.

 

Ultra sonic: Ultrasonic welding uses an acoustic tool to transfer vibration energy through the plastic parts and into the weld area. The friction of the vibrating molecules generates heat, which melts and welds the plastic. When the plastic reaches a molten state, vibration stops. Apply pressure while the molten plastic solidifies. Use this system is to weld smaller manufactured parts together.

 

I wonder if this generates enough heat to cause immature toning to coins after a period of time? I know this was a topic that Mark had posted in regards to slab toning.

[WoodenJefferson]

I posted this in my topic "NGC slabs are hermetically sealed". It would also work here.

 

So I would presume this would be the method for sonic sealing slabs.

 

Ultra sonic: Ultrasonic welding uses an acoustic tool to transfer vibration energy through the plastic parts and into the weld area. The friction of the vibrating molecules generates heat, which melts and welds the plastic. When the plastic reaches a molten state, vibration stops. Apply pressure while the molten plastic solidifies. Use this system is to weld smaller manufactured parts together.

 

I wonder if this generates enough heat to cause immature toning to coins after a period of time? I know this was a topic that Mark had posted in regards to slab toning.

Since your on a level of molecular bonding by using ultra high frequency sound waves as a mechanical means to generate heat through friction, I doubt seriously that enough heat would be generated to affect the contents.

 

However, during this excited molecular bonding, there would be a small amount of chloride gas released as a result. How much, I don’t know…could there be enough chlorine released to alter the encased contents, hard to say and hard to measure, but could be done in a laboratory with the right equipment.

 

There are some pretty smart cookies who post here (those college edumacated type) that could possibly shed more light on this particular subject.

 

Who’s going to pay to find out, not us…so for now this is pure speculation.