Displaying Coins and Sunlight

Hello All,

I am fairly new to this coin collector thing.

I have a windowsill that I was thinking of using for display purposes of some of my collection. Said windowsill is under a covered patio, and so the coins would never be exposed to any *direct* sunlight. I contacted 4 local coin stores, and got 2 "yes's" and 2 "no's" on the question of whether or not coins will be harmed by perlonged exposure to indirect sunlight.

Not being terribly satisfied with a 50/50 split on the answer, I thought I'd pose the question here instead.

Thanks

 

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As long as the coins are encapsulated where they won't be exposed to moisture, they should be okay. If you have them in a wooden box, then you would have to be concerned about gases affecting the coins. Sunlight won't affect them like they would banknotes.

I can't think of anything else, but wait for a few other opinions.

 

Indirect sunlight is still sunlight. Any harm to an object that can come to an item being displayed or put in direct sunlight for a prolonged period of time can also be affected to some degree by being displayed or put in indirect sunlight. It may be to a lesser degree or take a more prolonged period to show its effects but the root cause is still there.

 

Put a coin on your car's dashboard for a few weeks and watch what happens. The same thing will happen to coins exposed to indirect sunlight, though at a slower rate.
Guy

 

I don't think it's the "sun" that is causing what you're describing. It's likely a combination of the chemicals (plasticizers) leeching from the dashboard, and the heat generated by the direct sunlight.

Your biggest enemy for damage to coins will be gases and chemicals in the air. Different metals react differently. The other biggest enemy of coins is heat. Light itself (i.e., photons) will not damage coins that I know of; however, side effects of light like heat and it's interactions with plasticizers, etc. can cause major damage to coins.

Questions for you:

1. What kinds of coins are these (composition, encapsulated/graded, etc)?

2. What is the value of these coins? If they are displayed for "interest" and have little numismatic value, then I wouldn't worry too much either way.

 

All of the coins are encapsulated. Either individually, or as a set in their original mint packaging. The majority of these are silver, either Liberty Eagles, or the Canadian version, one of the 5oz National Park coins. There's also some colorized quarters, a few of the yearly mint sets (penny, nickle, dime, etc), and a 1/10th ounce gold coin. So in short, things that have some value, but nothing worth thousands of dollars.

The impression I had been under is that as long as everything was sealed, I was good to go. I seem to be hearing some oppinions here leaning that way as well. No actual ray of sunlight is ever going to get within 15-20 feet, and these are in a temperature-controlled house, so the temperature gradient will be minimal.

 

If they are displayed in a temperature controlled house, with no direct sunlight, I don't see much reason to worry. So long as there is not a heating/cooling register affecting their temperature by direct exposure. I say, display them away! When you get them all on display, snap a digital photo and show them off here too!

 

Indirect sunlight produces heat over time. All light produces heat.
Guy

 

Yes, but isn't the point that the heat interacts with the surrounding air, and *that* is what causes problems? And if the coins are encapsulated, it reduces interaction with the surrounding air to minimal possible levels?

 

If no ray of sunlight is going to get within X number of feet, then it is not in direct or indirect sunlight. But if when the window is open (as in shades not drawn or blinds not down, and blocking sunlight completely) then sunlight does come in, the area is in sunlight (indirect), so it does get within X number of feet. It will eventually have an effect on the coins.

It is the LIGHT source (even artificial light) which contains UV light that can break down the surface of any item. Direct sunlight, where an item is exposed not only to the UV rays but also to the wind and weather will break down first, but items exposed to UV light frequencies will break down regardless of the source of the UV light. It is not the HEAT from the light source but the wavelength of the light source, which as we know it is the UV spectrum, that is harmful to items over the long run. There may be other wavelengths of light also harmful, but the most common that people realize does harm is the UV spectrum. Eventually, ANY light source will harm an item, but it is generalized that artificial light sources are ok, as the length of time it would take to harm something with artificial light is a very long period of being exposed to it.

Even in museums, which display items in the light, the exhibits can be either rotated out of use, and stored better, or they are "cleaned" or "conserved" depending on the museum.

 

What does UV damage look like? I have never seen a graded coin referenced with this problem regardless of age. If anyone has one, post it.

 

Most museums use the Reciprocity Law when it comes to light and the collection within that it effects. It states that degradation is dependent on the amount of light and the length of exposure, and that there is no level below at which light is inactive. Damage is cumulative over time. So they regulate exposure to even the dimmist of lighted artifacts, including coins.

If sunlight was good for coins I'm sure we'd see a few outdoor shows during the spring and fall.
Guy

 

I just wonder why the silver coins i find with a metal detector never show they are damaged and one would think they had to be exposed to sunlight air temperatures and all outside eleaments?Yet the clean up nicely mostly just being washed or rinsed off.Pennys and nickles or clad coins are a much different story.

 

from

http://www.onepetro.org/mslib/servl...E-03090774&soc=NACE&speAppNameCookie=ONEPETRO
"The effect of ultraviolet light on the corrosion rates of different metals was studied in two separate investigations. Metal samples were immersed in a flowing fresh water discharge stream for either three or five months under both ultraviolet (UV) light and dark conditions. Weight-loss results demonstrated that pure zinc, carbon steel, aluminum 6061 (UNS A96061), pure copper, and pure silver all experienced photocorrosion, that is, a greater weight loss under exposure to UV light vs in the dark"


In the above quoted material...."greater weight loss" equals loss of metal.


Photocorrosion is simply corrosion of metal due strictly to the photo (light) source, or light spectrum, irregardless of heat or other items. UV light is not seen to the human eyes, but if you take the damage to skin (sunburn/cancer, down to the bones, at times, and eye damage from UV light), then abstract that out to encompass a harder denser material, like coins are made of, and realize that nothing is impervious to this. Most of the time things fail (metal stress, failure) due to combinations of stressors, and not just the UV, or erosion of materials happens concomittantly and erosion is blamed solely, because erosion can be "seen" and UV damage escapes the "blame". It is hidden damage.

 

I assume you are referring to ART museums and museums with PAPER documents? I have never seen any reference to UV light causing any damage to coins. Moisture, gases, and heat --yes. Light itself, never. Light will also interact with the plastics in whatever holder you use, but might you reference some science or chemistry that would support that light has an effect on metals? Not trying to be polemical, I honestly want to know.

 

I'm surprised that nobody has brought up the real threat to coins being displayed in this manner. Eventually someone that sees your display will decide they could make better use of it or innocently make a comment about it to someone else that thinks the same. Displaying coins anywhere near a window invites a "smash and grab" type scenerio. there's a chance the coins will be long gone before the sun cam do any damage to them.

Richard

 

I'm going to go out on a limb here and say that it's likely more the WATER that caused the corrosion than the light. Any studies relevant to coins which are stored in a DRY, temperature controlled, non-gaseous location but with just photos bouncing off of the metal? BY THE WAY, UV rays do not penetrate ordinary window glass very well. Thus, why your photo-change "transitions" lenses do not work when you are in a car. so if it's just "ultraviolet light" that is the problem, and not just photons in general, I'm not seeing the relevance here.

If nothing else, your gold is obviously fine to display. If these were "multi-thousands-of-dollars" of coins on display I would think a bit more about the question, but they seem to just be run-of-the-mill coins worth a reasonably small amount, put on display for enjoyment.

 

Ummm.. not entirely true. Chemiluminescent light doesn't create, produce or cause heat. Example, fireflies use this method to create light but there is no heat produced.

Also, light itself does produce or create heat but just depends on the circumstances in how you're describing light creating heat. Light will excite the electrons in the atoms of whatever the light is hitting called radiationless transitions to vibrationally excite them, which in turn creates the heat we feel.

 

I was going to say what Ziggy just said, but I had to read through everything first. There is nothing like advertising to all who can see that you have collectible coins in the house.

Also, if you don't think indirect sunlight will do any harm, just ask the people who go fishing on a boat all day long who can't understand why they got severe sunburn because they were under the canopy on the boat.

Chris