Bronze disease vs. verdigris

I noticed many green, powdery areas on a pair of brass / bronze candelabras after washing them. The candelabras are and were very patinated even before that happened. I didn't think much of it until I read about bronze disease and verdigris (which are different things).

According to sources, water, sometimes even a humid day can trigger bronze disease in any copper-based item and corrode the piece away completely. Green powder is the first noticeable stage. In some cases it only takes months for it to corrode through. It apparently can also contaminate other copper based objects due to the chemistry of it all.

Take a moment to read about bronze disease: https://www.brown.edu/Departments/Joukowsky_Institute/courses/greekpast/4867.html

I have a bundle of questions about this:

Why did I only hear about this now?

Why aren't all bronze items corroded with bronze disease if moisture is what causes it so easily?

Most information about bronze disease is within the ancient coin collector community. Why haven't I heard of any antique lighting fixtures usually having bronze disease?

What should I do about the candelabras? Is it safe to keep them near other bronze items? I'm not interested in playing chemist at home and bathing the candelabras in chemicals for weeks to maybe slow down the bronze disease, like one of the websites suggested.

Should I stop buying any copper based metal objects in the fear that bronze disease will ruin them?

Is there a "disease" for every material? What's next a porcelain flu?

 

We need to see photos of your items. Furnishing items like yours very rarely suffer from bronze disease. First thing I’d do is try to verify your items are bronze. We get countless guests posting about their “bronze” here which is actually Plated spelter. Spelter often breaks out with areas that have oxidized into powdery zinc oxide (white.)

 

Both items are brass or bronze. I say both because I noticed another candlestick (also with a strong patina) that has some green, although less so. It's been there for a while I just never thought it was something dreadful.

The second picture probably looks exactly like spelter, but it's not. Only very dark patina, whether artifically applied or due to storage conditions.

 

Do people generally avoid items with green powdery spots then? Is it something I should be considering too?

 

From Wikipedia "The patches of bronze disease can be scraped off the surface using a fingernail or a wooden pick. These properties are all in comparison with verdigris which is normally a duller shade, uniform across the whole of the affected object, and cannot be scratched off with wood or fingernails. Unlike bronze disease, verdigris serves to protect the metal."

This is very confusing. How do I know what's verdigris and what's bronze disease, especially in pictures?

 

The way coin collectors know about bronze disease, serious shell collectors & conservators of anything calcium carbonate based are well aware of something called 'Byne's disease', which is really another oxidative/corrosive process. Obviously it can just as easily affect shell cameos, but most in the cameo world are unaware of it. It requires prolonged storage with enough atmospheric humidity & a material, such as oak or cardboard, that provides the necessary molecules to make acetic or formic acid. It cannot be reversed, just addressed so that it does not spread.

 

I think it's incredibly depressing that there isn't almost anything that's surely safe from permanent decay or corrosion. On a wide scale, ceramics and wood seem to be the best bets, so to speak. Wood of course decays in many ways but it's often easier to recover and repair than something you can't do anything about, like what you mentioned.

 

interesting topic, I have a number of items with green stuff on them. Including this massive sanctuary lamp which after many failed attempts still shows greenies. Hope it is not bronze disease...

 

This is embarrassing, I guess my earlier post didn’t state it correctly. We need to see the whole item please, it tells us things that are hard to itemize, all the better to help you with, my deah!

 

In first pic, what are the black or dark grey areas please?

 

The bronze Rainey Memorial Gates at the Bronx Zoo have been in place since 1934. Guess this is an example of the oxidized copper providing a protective patina.





They always remind me it's just turtles all the way down.

 

You could get some useful info by scraping a small sample of the powdery stuff and having a commercial lab do a qualitative analysis of it, first checking for zinc compounds. I’ll probably have you convinced I’m a magician if the lab finds zinc oxide or a zinc salt like zinc chloride.

 

Thanks for all the interesting comments and advice, everyone. I for one recommend this article I read by the Victoria&Albert museum: http://www.vam.ac.uk/content/articles/c/caring-for-your-copper-brass-bronze-and-other-alloys/

 

If I'm looking at the right picture, those are dark spots on the surface of the fixture. I don't know what they are.

 

Will we ever get to see the whole item?

You might want to get an experienced restorer to look at the item; they can tell you a lot while doing your free estimate.

 

I actually panicked about the corrosion and decided to polish the candle holder. It's still mid-polishing and elsewhere but I'll take a picture of the final product next week when I continue it.

 

We went there quite often when I was a kid - I LOVED that zoo!

Have you seen this old PC? The picture was obviously done before the oxidation!

 

If you went there now, you would find it very changed, although the gate, the fountain & the original buildings are still there. Most of the buildings now have caged humans, except the big cat house, which has become Madagascar. I go mainly to spend time with the gorillas. Watching 5 little ones that range from 3 1/2 down to 1 1/4 is very good for the soul.