There have been several posts in the past about the use of a preservative micro-crystalline product that museums use to preserve metal objects, including coins. Its use engenders debate in the numismatic community about its effects, though museums seem to like it. Whether it does actually protect coins from future ravages of time, well, I suppose we will have to wait a few centuries to see if that is so. Also, there are some who believe the use of micro-crystalline can improve the appearance of coins, giving them a smoother, glossy look. I suppose that will be up for debate as well since eye appeal is about as subjective a determination as there can be. In reading about micro-crystalline I have not found any before-and-after pictures, so I decided to take a handful of coins and apply the substance, wait a bit and gently buff the coins with a soft cloth to see if it is possible to discern any difference in appearance. What I found out is that I can see no difference at all with silver coins so I have not included their images here. I tried four low silver billon coins and included below are two of them, the Roman eastern mint Tetradrachmas, and I am not sure if there is any difference. I tried two brass pieces, both Dupondii of Vespasian, and one of the coins is pictured below. The small bronze of Commodus below may also be a brass but I am not sure. I think I may see a slight improvement in appearance there. The Sestertius of Alexander Severus and the bronze As of the same ruler do seem to me to look better as is true of the little Tetricus (or Claudius II) and the Kushan bronze from First century India and the big Follis of Justinian. What I would like readers to do is to take a look at my photos and see if there is any detectable change in the appearances of the coins from before to after the application of the micro-crystalline. Also, for those of you who may have been using this substance for a while, what is your experience with it? Thanks for any input you might have.
I'd certainly say: be careful what you put it on - here's an illustration. I decided to experiment with this coin - a little Ren Wax on a soft toothbrush. Something black and inky came right off with a few brushes and drying with a cloth. Some may see this as destruction of a nice sand patina - I was surprised by the amount of black gunk that came off in the wax- made me wonder if the patina had been added recently. here's a little more detail: I don't dislike the end result - but it leaves me with the general thought that I wouldn't experiment on a coin that I liked. Maximianus Herculeus, (AD 286-305), Antoninianus, Antioch. Obv: IMP C M AVR VAL MAXIMIANVS P F AVG Radiate and cuirassed bust right. Rev: IOV ET HERCV CONSER AVGG / S, star above / XXI in exergue, Jupiter standing left, holding scepter and globe, facing Hercules standing right, holding Victory, club and lion’s skin. Ref: RIC V 622 date AD 285-295
I suspect any waxy substance would make almost any circulated coin look better, but the question should be ; what happens when these saturated hydrocarbons (lipids) start to break down over time ?. You can get all sorts of short chain hydrocarbon compounds produced depending on environmental factors. I am sure it depends a great deal on the company producing the product. I can't imagine the museums that use this on coins and metal haven't produced reports or at least guidance for replacement. It is similar to paraffin except it has smaller wax crystals and I am not quite sure why that is important for coin storage as the chemistry is quite similar. IMO, Jim
I see your point. On any silver coins I have tried it on, nothing came off and actually nothing at all seemed to happen. If the material has formed a barrier to future corrosion the barrier seems invisible. On the bronze and brass nothing came off of the coins when using a tiny paint brush (the kind I use to paint model figures). Only when I buffed them, gently, did a very slight greenish to blackish stain come off on the soft white cloth I was using. The only way I could determine that the micro-crystalline was applied was that on bronze and, to a lesser extent on brass, was that they seemed a bit glossier. I totally understand reluctance to use the material on my better coins, at least until I can obtain actual hands-on experience with the experience of other coin collectors who have used it. As I said above, museums seem to like the material but their concerns and goals may be different from those of hobbyists who I would like to hear more from. Thanks for you information and I hope others will relate their experiences, perhaps with their own before and after pictures and analysis.
In the past, when I was beginning to collect, I have used Ren Wax with mixed results. Some surfaces certainly looked better after applying it. Yet, sometimes the wax layer also made details and outlines appear less sharp and even seemed to contribute to an outbreak of bronze disease, maybe because of moisture trapped in the coin. The Nero below is an example of the latter two effects. The profile looked sharper before applying Ren Wax. After being treated with this substance, the coin developed a bit of bronze disease around the edges, which I fortunately recognized early on and was able to stop/stabilize with a long bath in an alcoholic benzotriazole solution. The main reason I stopped using Ren Wax is that there doesn't seem to be any way to remove a mycro-crystalline wax layer without inflicting great damage to the coin. Acetone baths etc. won't dissolve it. Since they are irreversible and because I don't know what long term effects they will have, for example whether such coatings might break down, become sticky or change color, I decided to stay away from any mycro-crystalline products. Nero, Roman Empire, as, 62–68 AD, Rome mint. Obv: NERO CAESAR AVG GERM IMP, laureate head of Nero right. Rev: S-C, Victory with shield walking left, inscription on shield (SPQR) worn away. 28mm, 11.09g. Ref: RIC I, 312. Ex André Cichos.
Thanks for your experiences. Museums who use this material seem to like it. Are there any examples from them that indicate potential problems? Interestingly, there is a coin business operating on a web site that says they routinely treat their coins upon sale with micro-crystalline before they send them out.
