A couple of days ago in my local coin club I came across an article in a German coin magazine describing the treatment of bronze disease with a laser, such as used by dentists (or ophthalmologists). There were striking pictures of a coin (unfortunately I have not been able to find them on the internet) before (with encrustation of cupric-hydroxide around the digit 5) and after. After zapping the coin a couple of times from the right and a couple of times from the left, the encrustation was completely removed, with no apparent trace on the coin. Obviously, the coin wasn't very far gone to begin with (otherwise there would have been pits) but I found the idea ingenious. Apparently the laser is designed to blast away anything containing water (as does copper hydroxide). The writer went on to speculate about the eventual price of such commercial treatment, concluding it would run to 100-150 Euros per coin, which would rule out doing this on a routine basis, but if any of you have a dentist friend who would be willing to let you play with his laser machine (priced around 20-30 thousand Euros) for half-an-hour, and have some afflicted coins, it definitely sounds worth a try.
Lasers can also be used, in fact are used, to deceptively alter coins and remove/repair hairlines, scratches, contact marks so that they be graded higher than they deserve to be graded. But it is important to note that such alteration with a laser can be detected by those with the experience to do so. I suspect that the work you describe with lasers can also be detected.
Is this how they "repair" coins? I recently saw a pattern seated dollar in a slab (it had no stars above Liberty's head). The slab-tag said "REPAIRED". I couldn't see ANY sign of a repair at all(!) It was pretty cool. It was supposed to have had a hole driven into it, if you can believe that. Can you imagine someone driving a hole into a pattern seated dollar?
Not usually no. Most of the time when a laser has been used on a coin it will be referred to as having altered surfaces. Yes I can easily believe it. Pattern or not, it used to be pretty common to do that so it could be worn as a necklace. And the vast majority of the time when a coin is noted as having been repaired they are referring to a hole having been filled.
Quite possibly, but it sure looks better than a coin with bronze disease--and hopefully will no longer corrode, if properly cared for. I wasn't recommending falsifying coins, but I'm always interested in getting crap off the surface.
I wasn't sating anything negative about the practice of using lasers on bronze disease, that's why I used the word "also" in my comments. But if what you want is to get spots of verdigris off your coins, there is a much cheaper and simpler way to do it than using a laser. Just buy yourself some Verdi-Care, it works.
My dad's a dentist I'll give it a try and post before and after pictures Sent from my iPad using Tapatalk HD
I've got Verdi-Care and use it to protect coins in good condition, but doubt it will actually remove an encrustation of verdigris all by itself. The pictures shown in the Verdi-Care-Typical-Results pdf show some improvement, but not complete removal of the verdigris, whereas the pix in the coin magazine showed absolutely clean metal after the laser treatment (but still with patina).
Yes, using Verdi-Care is a matter of degree. If a coin is completely covered in verdigris or nearly so then Verdi-Care is not going to do much. And I have my doubts if a laser could do it either, but I don't know. But what you described in your original post was a spot of verdigris being removed by a laser, and that Verdi-Care can do.
The laser would be selectively focused on the verdigris and could vaporize it if properly tuned. It would not affect the patina on the rest of the coin because the laser would never be on those areas. But the ares where the verdigris is removed should NOT show the same patina. Verdigris eats into the surface of the metal, if you remove the verdigris there would be either bare virgin metal, or metal "scorched/discolored" by the laser. I would imagine the treatment works by tuning the laser to a frequency that the verdigris absorbs strongly, and which the metal does not. When the laser is shown on the verdigris it absorbs the energy and vaporizes. The heat of vaporization may discolor the underlying metal.
