Treating bronze disease in an ancient Egyptian antiquity

A couple of months ago, I saw a small bronze ancient Egyptian Apis bull for sale at a gallery where I've been making occasional purchases for almost 15 years now:



I've wished I had an artifact like this one for years, and the price was in the affordable range for me. Plus, it's intact except that its left ear is missing -- it's unusual to find these without one or more missing ears, horns, or feet, or without the uraeus broken off the sun disk. However, when I looked closely at the photos on the website, I saw a lot of suspicious-looking pale green spots on both sides:





I wondered if the spots might be signs of bronze disease, since I saw no reason why it can't occur in bronze artifacts as easily as coins, even though I'd never encountered it. So I emailed the dealer and asked if that's what the spots could be, and he wrote back to tell me that indeed, the bull had active bronze disease which he'd intended to get treated after he bought it last year, but that doing so fell by the wayside along with a lot of other things during the pandemic. I told him that I might still be interested in buying the bull if he had it treated, so he said he'd send it to a professional art conservator he uses, although she was very busy and might not get to it for a while.

A couple of months passed, and the dealer responded to my inquiry by telling me that the conservator had finished the job and returned the artifact to him. So I went down to his store in midtown the other day, and he showed me this report:


Here's a link to her background and qualifications: http://artconservationatelier.com/bio/.

I'd be very curious to know if her methods sound familiar to those of you who've treated BD in ancient coins, and are anything like what you might have tried yourself.

He showed me the bull as it looks now, and although many of the same spots are still somewhat visible, they're no longer flaky and don't look as "angry" to me as they did in the "before" photos. And I still really liked the piece overall. If the conservator had dug out the green spots entirely, there would probably be pitting all over the place. The dealer gave me a 20% discount from the price on the website (which I had been prepared to pay), and told me to bring the bull back in if the bronze disease showed any signs of recurring. So I bought it, and took it home. (No shipping charges!) Just in case, I'm keeping it in its own individual miniature glass dome, so nothing can spread to my other bronze artifacts kept on the same shelf.

Interestingly, I didn't realize, until the dealer showed me, that the bull was made with an integral peg for inserting into a base. (Obviously, the wooden base it has now is not the original one; it probably dates to the 1950s or 1960s!)





Note that the green spots are still there, but less visible in hand than in the before photos; the most prominent one still visible is on the right flank.

Here are the sun disk and uraeus, which you can't really see in the profile photos:







On the left side, the only green spots I can really still see as very noticeable, even if if I dial up the contrast all the way, are on the insides of the right foreleg and back leg:



However, even though they don't look bad in hand, the green spots on the right side are still all quite visible when I dial up the contrast all the way:

[cont]

 

Log in or Sign up to hide this ad.

Right side, with contrast at its highest:



As I said, there's no flaking. Should I just leave it alone, or is there anything else any of you would do to "treat" it? I don't have to worry about contagion -- it lives in its own little glass dome:





Finally, for comparison purposes, here are two other examples of bronze Apis bulls, both almost exactly the same size as mine, both sold by a dealer in Montreal for a little more than what I paid:





Many thanks.

PS: My bull really does have a scarab with wings and beetle horns incised on the tail end of its back, as referenced in the description, but I've found it completely impossible to photograph. Even the blanket looks more like scratches than a blanket in photos.

 

A really cool artifact Donna! Super cool. I was able to see a giant Egyptian Apis bull statue here in Minneapolis at an exhibit at the Minneapolis Institute of Arts. It was so well preserved, it looked like it was made last week.

As for the suspected bronze disease... I think the best course is always to first watch and see. I have a few coins that have what looks like bronze disease or spots of brighter green but have had no change or active corrosion in nearly 10 years (so it may not be BD). I’d research a course of action but photograph it and just watch it. If there are not changes, leave it as is. If there are changes, do what you can.

 

Wow! I've never seen one close to that size before. As for the green spots, it isn't that I really suspect bronze disease at this point. After all, it was just treated by a professional. I guess it wouldn't have been realistic of me to expect her to get rid of those spots entirely, without leaving pitting. You're probably right that I should simply keep an eye on it in the future.

 

Yeah it was amazing, maybe 7ft tall (on its base)! It was with a traveling exhibit of artifacts found in a sunken city. The exhibit was well worth seeing. Here’s the information from the exhibit book:

 

Interesting results! I feel like the color could have been even out a bit more cleanly, but I've only experimented on one case of BD so it's hard to say.


Close up of major BD on head:
I was able to turn the green color into a brown that matches most of the rest of the surface.

 

I've never heard of treating BD with sodium carbonate before, but I assume the conservator knows what she is doing. Many people in this forum have talked about treating BD with sodium sesquicarbonate. My guess is that the reaction is similar.

If it were my bull, I'd leave it sitting out for at least 3 months--on display, under glass is fine--before doing anything to it. Then, if you wanted to add another layer of protection, give it a coat of Ren Wax.

Congratulations on your new acquisition. That's a very interesting and impressive artifact.

 

That is a very beautiful piece! I really like it.

The method used to combat the bronze disease is a fairly standard one. Benzotriazole is a very effective barrier coating for bronze. It bonds chemically to the bronze and protects it from oxidation. It is fairly toxic though but not as much once it is bonded to metal. I would put a few desiccant packs and a humidity meter inside your dome and make sure the humidity stays below 40%. Then it should be fine. Moisture above 50% is what activates bronze disease. With the treatment it has had and a low humidity environment I think it should be good almost indefinitely.

John

 

Very informative on the bronze disease treatment process as well as the Apis Bull. Thank you Donna.

 

Wonderful piece of art @DonnaML ! Really a beauty!
About BD treatment it’s new to me to read using sodium carbonate for neutralization, also a 1 minute time looks weird. I treated several coins with sodium sesquicarbonate for 2 weeks, changing the solution.
I think you have to do nothing but control time by time, BZT is usually a game ender.

 

Excellent presentation...!

 

I personally would not put it in a glass bowl with desiccant. I would want to be certain that the BD is gone.

 

Just out of curiosity, what would you do to make sure it's gone, beyond keeping an eye on it in the future? Remember that it's not really just a glass bowl; it's a fairly airtight glass dome that's only about 4 inches in diameter.

 

Fascinating. I wonder if they've actually found hundreds of huge mummified bulls down there.

 

Thank you. I ordered some 1-gram desiccant packs that ought to be small enough to fit one or two inside a 4-inch diameter glass dome, without being ridiculously obtrusive. I wonder if a humidity meter like these would be small enough to fit inside: https://www.amazon.com/Veanic-Elect...uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl

It's certainly not humid in NYC now, but it does get quite humid in the summer.

 

That is pretty similar to the meters I got.

Maybe get a larger dome for it if needed?

I find it reassuring to measure what the humidity level is versus guessing.

John

 

Yes, after reading people write about treating BD by putting it in various solutions for weeks at a time, a 1-minute immersion did seem rather fast! I'll just assume that she knew what she was doing, that the Benzotriazole for 24 hours is what really did the job, and that as long as I keep an eye on it I can catch any recurring BD in plenty of time. Either by bringing it back to Hixenbaugh so his conservator can re-treat it, or, if it happens 15 years from now and the store is no longer around, by finding someone else to treat it or doing it myself.

I should make very clear, in case anyone thinks I sound like I already have regrets, that I'm very happy with the bull. It's a wonderful little artifact. I wouldn't have bought it if I'd had any kind of bad feeling. Not when I spent more on it than I've ever spent on a coin, and as much as I've ever spent on any other antiquity! (I paid about the same for a couple of my Attic black-figure lekythoi.) Tastes may differ, but between you, me, and the lamppost, I like it as much or better than either of the other small bronze Apis bulls that were recently available, shown in the two photos above. Even if it's not in the same class as some larger examples like this one available at Hixenbaugh for $9,300 (see https://www.hixenbaugh.net/gallery/detail.cfm?itemnum=7302), or this one sold at Christie's for 16,250 GBP (see https://www.sothebys.com/en/buy/auc...-egyptian-bronze-figure-of-the-apis-bull-26th).

 

I'll see if something like that fits. I suppose that if it doesn't, I can always follow your suggestion and put the bull in a larger dome with one or more other objects, as long as they're not made of bronze!

 

Nice antiquity, Donna.

As far as the green spots are concerned, keep an eye on them. If they are active (powdery and growing), then the area or areas need treatment to neutralize the process. If the seller is willing to take it back for treatment, that's what you should do, since the treating will be done, I assume by a professional restorer.

Overall the object seems to have a very nice patina, so once the BD is dealt with, those treated areas should blend in over time.

Bronze disease is especially active where there's a lot of humidity, so you might consider keeping the object in a dry environment.

 

Her treatment sounds spot on, I usually do 3 parts sodium carbonate to 1 bicarbonate but repeat 3 times once a day and letting soak and maybe a light scrub inbetween. I usually use 99 isopropyl instead of acetone. After the Benzotriazole i usually ren wax to be safe but thats me. This treatment will remove fake patina. I did post this before but for the context I think it would be kosher to post again


Thats after a year. I do have to treat below the bust again but the real bad spot was above the head. It was in bad shape when I got it. Now not everyone agrees with my treatment but I tend to follow my own path.