TheLaw of Unintended Consequences

[£400 for a Penny ?]

Sorry to harp on about the preservation of lustre on bronze coins, but I have a few and I want to make sure that I'm doing the best I can. My next question is about the practice of keeping a naked copper ingot with one's collection to act as a 'bellweather' for the presence in the environment of any 'nasty's', as I have seen mooted as an extension of the intercept shield principle.

Sounds a good idea, but not being a metallurgist I don't know if it would be drawing potential toning agents away from the coins or as the title of this thread alludes to, acting as a base camp for them to get established and wreak havoc i.e achieving exactly what I set out to avoid in the first place.

Any views ?

[VickySilver]

Now that is a thought, but never have heard of anyone doing it. Most probably do not check their collections by the day or week, so whatever corruptive influence at play will have begun to run its course before the collector is able to do much. In other words, the naked copper as you put it will show some evidence of these oxidants and the like but may not be all that helpful in that what chemical activity taking place has already taken place.

It should not be able to "sacrifice" its own oxidation and spare the collection although a "lesser" metal in close confines to a more "noble" metal will be consumed by the oxidative reaction first; on the other hand, this process is not like an infectious disease - that is, if the copper exposed begins to turn it will not increase reactions to the coins about it.

Many people put dessicants in with their coins and this will draw some of the moisture away from the microclimate about the enclosed coins. As you know moisture will tend to accelerate chemical reactions (as will heat), and so that is a good idea. The Intercept Shield idea incorporates some of this, but I must confess that I do not have knowledge to the exact details of this company's products.

[Peckris]

"Many people put dessicants in with their coins and this will draw some of the moisture away from the microclimate about the enclosed coins"

Silica Gel is the normal thing used for this - a good reputable chemist should be able to either supply you with some, or at least let you know where you can get some.

The other thing to research is the effect of using a light non-reactive oil on a lustre coin, applying it very very lightly with a micro-cloth of the sort supplied by opticians for cleaning glasses. There is nothing better than oil for keeping out pollutants but it should be very carefully researched first, and practised on a few modern BU bronze pennies of no value.

[VickySilver]

I am not convinced that oil application is the best idea as there are all sorts of oils, some with mildly acidic properties. Another issue is that in this polluted modern environment that most of us live in features many organics that may utilize the oil as a solvent and gain a better access to the surfaces of the coin - this even in paper envelopes, 2x2s or mylar holders as these are airborne. I remember being amazed by the concept of vapor pressure exerted even by seemingly inert substance such as metals or plastics, and so we know that everyday exposures to our coins (let alone ourselves) occurs with such compounds as the bonding agents in carpeting.

How important are they? Probably nobody knows for sure and varies a good bit.And different from place to place.

[Peckris]

I am not convinced that oil application is the best idea as there are all sorts of oils, some with mildly acidic properties. Another issue is that in this polluted modern environment that most of us live in features many organics that may utilize the oil as a solvent and gain a better access to the surfaces of the coin

Yes - this is why I stressed both research and experimentation on low value items.