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The mission of the Brooklyn Museum is to act as a bridge between the rich artistic heritage of world cultures, as embodied in its collections, and the unique experience of each visitor. Dedicated to the primacy of the visitor experience, committed to excellence in every aspect of its collections and programs, and drawing on both new and traditional tools of communication, interpretation, and presentation, the Museum aims to serve its diverse public as a dynamic, innovative, and welcoming center for learning through the visual arts.

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About the Mut Expedition

Since 1976, the Brooklyn Museum has been carrying out archaeological work at the Temple Precinct of the Goddess Mut at South Karnak, an important religious site for almost two thousand years. Dig Diary invites you to follow the recent work of the expedition in weekly photo journals covering every aspect of our team's activity.

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Saturday, February 24, 2007

Coins

Almost everyone, who has ever worked with archaeological objects, or on a dig, has a coin story. It usually begins like this, "I was told to put the coins in some chemical...", and then after a certain amount of hours or days, depending on whether the person forgot that the coins were in "some chemical", the coins are gone, having disappeared or dissolved into the bath.

Cleaning corroded metal objects is hard work. Think about it. Most metal objects (unless made of gold or silver) start out as ores, such as copper carbonate, or copper sulphate. In other words, objects made of metal start out as corrosion, and only after a lot of human intervention do they become metal objects. So, after several thousands of years of being buried in the soil, these metal objects want to revert back to corrosion. It goes without saying that, after discovered by an archaeologist, it usually takes a great deal of intervention on the part of the conservator to get to the metal surface. Yes, chemicals are one way to assist in changing the corrosion, so that it can be removed to possibly reveal a metal surface. Sometimes there is no metal core, below all of the corrosion. The object is completely mineralized. Mechanically removing the corrosion is also a safer, but often very time consuming and physically difficult process. At the site, this year we are trying a mild solution of EDTA (ethylene diamine tetra acetic acid) made basic with ammonia. It has proven to be helpful at softening the corrosion crusts, making the mechanical removal with a scalpel more effective, and safer. The solution turns blue as copper corrosion dissolves.

When the archaeologists register the finds, as Jaap is doing in this photo, it is much more useful to have an actual image on the coin, or other information that may help in dating a layer. This is why finding coins is often exciting, yet painful at the same time. Luckily however, unlike the corrosion that Jakki mentioned in her post on the Wadjet Figure, the corrosion crusts at the Mut Temple are mostly stable.

Lisa Bruno, Objects Conservator

1 Comments:

Anonymous Anonymous said...

very cool and meticulous work but well worth it when the coin is revealed...that's awesome

February 25, 2007 9:50 AM permalink  

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