When this small copper alloy bell was brought into the conservation laboratory for cleaning it did not seem any different than any of the other copper alloys from HSMC. Most of the copper alloy artifacts at HSMC are in good condition with core metal remaining. The cleaning process is straightforward, and involves mechanical cleaning of the surfaces under the microscope. Upon investigative cleaning of the bell however, we discovered something inside the bell. A small round iron clapper was still present inside the bell. The routine cleaning of this bell would suddenly take on a different direction.
When objects are composed of two or more materials they are referred to as “composites” in conservation. This is because the treatment of such objects will be different than that of an object which is only composed of one material. The bell would now be a more difficult treatment because the copper alloy and iron components would be cleaned differently. And the cleaning technique for one of the materials could potentially damage the other material. Conservation treatment of composite artifacts are more complicated and are always left to a professional conservator for this reason. Sometimes one of the materials is in much better shape than the other, and one of the materials may be sacrificed to the other to ensure the long-term stability of the entire object. This type of decision is not made without careful consideration, and the conservator will always lean toward the more sensitive and unstable material first for treatment.
Both the copper alloy and iron parts of the bell were in fairly good condition. This is very unusual as well. When dissimilar metals are in contact, a corrosion cell naturally occurs. The metal which is lower on the galvanic series (or the least noble metal) will corrode preferentially to the other metal. When copper and iron are in close contact and form this type of corrosion cell, the copper is always preserved much better than the iron. However, the iron in the bell remained in tact and contained a significant amount of core metal making it an excellent candidate for treatment.
The copper alloy part of the bell was cleaned in the usual manner. When the cleaning was completed it was time to clean the interior iron clapper which was heavily corroded and adhered to the inside of the bell. It was very difficult to get a tool inside the bell to clean the iron sufficiently. In the end it was decided to use a very small stream of air under low pressure to loosen the corrosion and release the clapper. Excess corrosion and dirt were removed from the interior of the bell using small blasts of air in localized spots. After cleaning, the bell was rinsed and degreased and left to dry. Upon moving the bell to complete treatment it was noticed that the clapper had loosened inside and “sound” was restored to the bell. While the intent of any conservation treatment is not to “restore” the object to its original form, especially artifacts whose historical integrity is tied to change during burial — this was as much a surprise to the conservator as it was to the curator. And one can’t help but wonder if the sound of the bell is close to its original or not.
This small bell was of the type and size often traded to the American Indians in exchange for furs, corn, and other commodities. The American Indians particularly valued copper objects and these were some of the most successful exchange items in the early Chesapeake.