And it's not a coin... A while back I posted my collection of Romano-British fibulae. Well, much to my horror, while inspecting them this morning I discovered that there were powdery green patches growing on my ornate silvered Hod Hill brooch, flaking off onto my shelf. You can sort of see them in this picture, circled for emphasis. There are many more smaller ones, and one particularly bad patch on the bottom. From the look of it, I imagine it's festered up before and been cleaned off, and may have been inactive for a while. This evening I sat down and cleaned it out with toothpicks and a dental pick (talk about tedious). I'm certain it's bronze disease, from the pitted appearance and the fact that the powdery material leaves behind yet more pits. Luckily, no holes, and there is a similar patina to the rest of the surface beneath the powder. I feel I have a sacred mission to save this beautiful piece for future generations. So for now I've removed the powder, and I am letting it sit on a lamp to hopefully slowly desiccate it. I am afraid to put it in an oven or do anything too drastic, as the remaining silvering looks quite fragile. For the same reason, I have not soaked it in distilled water as some have advised. I'll only get harsher if I have to; hopefully it's treatable with very conservative measures. If it goes a few weeks without coming back, I will coat it in Renaissance Wax to keep it sealed.
Yo Sept! Check out the link, maybe there's an answer on treatment. good luck! http://www.collector-antiquities.co...estoring-and-conservation/bronze-disease.html
I would wait at least 6 months before deciding its cured. Just set it out somewhere and check it every couple of weeks. Bronze disease can be re-initiated by moisture in the air, so it might not be enough to just dry it out. You need to neutralize the chlorine that has somehow started eating into your fibula. I don't know if simple heating can do this. It might, but if it comes back consider removing the chlorine either through chemical neutralization or repeated distilled water soaks. Good luck.
Still feeling very sad and worried about this one. Having read some of the articles, I am going to follow the general consensus and soak it in distilled water. It sounds like a bad idea, since moisture is the cause, but others who understand the chemistry better than I do (and have been through this before) recommend it, so I am going to do that. I suspect it's been treated before, or at least covered up enough to be not so noticeable. Luckily, all of the pits I've removed seem to reveal good metal underneath, so I don't think it's a lost cause. I just hope the soaking doesn't damage the silvering. I know that chemicals would probably do that, so I want to keep that as an absolute last resort.
Just an update; I have been soaking it in distilled water for about a week now. Every time I take it out I seem to notice more powder that I failed to eliminate, but I don't think it's growing. It's been incredibly painstaking, and with so many tiny holes (see the picture) I doubt I can ever remove every single fragment of the powder. Will soaking it for a while longer then neutralizing the moisture be enough to stop it? Still trying to save the silvering...
You might look into treating it with sodium sesquicarbonate. I've heard of people using it to treat BD. But I've never used it, and I can't vouch for it. I have no idea what it might or might not do to the silvering. But I wonder if you're being a little impatient. You said that the powder isn't growing, so what is your concern? The purpose of the DW is to remove all traces of chlorine. How often do you change the water? It usually takes me a couple of weeks to treat a coin. Your fibula is much larger and has many more nooks and crannies. I'd give it at least a month, changing the water every other day or so. You might also give it a light scrub with a toothbrush (no soap! just DW) once every week or two. It shouldn't take more that a minute or two to dump out the old DW and refill the container.
Sodium sesquicarbonate works. The recipes I've found on the Internet are poor, as those making them up don't seem to understand chemistry, but if you can get some sodium sesquicarbonate and make a 5% solution of it, it WILL slowly remove the bronze disease. You may need several changes of the stuff over a couple of weeks. If you leave the piece in until the corrosion is all gone and then put something on the surface of the piece to protect it from the air, your item should last a long time.
Well, the reason I asked about this is because I don't know if I'm being impatient. The instructions I find online are so contradictory, ranging from soaking for weeks to soaking for days. I'd taken it out last night to inspect while changing the water, and ended up poking at it to remove more powder. I just wonder whether the distilled water will actually remove the powder, or just make it inactive? There's no way I could mechanically remove every single fragment of it. Sodium sesquicarbonate remains an option as well, though I'd like to keep it as a last resort because of its possible effects on the silvering. But I do want to cure this once and for all. I appreciate everyone's advice. I'm also working on a coin with bronze disease, although it is extremely minor compared to this, and should be alright.
