AIC's 52nd Annual Meeting

Archaeological iron is well known to be prone to deterioration. Chloride ions accumulated in burial can cause aggressive, cyclical corrosion processes. If left untreated, in environments over 12% relative humidity, these corrosion processes can continue until the artifact is unrecognizable. Desalination methods are used to slow this degradation by drawing chlorides out of the object.

In The Colonial Williamsburg Foundation’s Archaeological Conservation Laboratory, a simple desalination method is used. Objects are submerged in a sodium hydroxide solution that is changed at regular intervals until the amount of chlorides measured in the solution decreases to our minimum level of detection. The artifact is then rinsed in deionized water and dried in an oven.

This treatment can be intense for objects, particularly if they are in a fragile state. Over the years, conservators have noticed that artifacts that are small or have areas that are thin and delicate, can unexpectedly fragment during this process. This deterioration can range from small fractures to full areas of detachment, and is not always predictable.

Staff wanted to find a way to reduce potential fragmentation while still allowing fragile objects to undergo the crucial treatment step of desalination. After several test rounds, conservators have adopted a method of lining susceptible objects prior to desalination. A piece(s) of fiberglass tissue is adhered to one side of the object with Paraloid B-72 to provide support. The lining remains on the object throughout desalination, rinsing, and drying. It can then be removed with acetone brushing and tweezers. For very fragile artifacts, the lining can be replaced and serve as semi-permanent support.

This method was shown to provide adequate support for objects of varying sizes and prevent fragmentation. In cases where fracturing did still occur, the fiberglass tissue retained the original location of the fragments allowing for more accurate reassociation after drying. This poster will fully outline this technique as well as provide examples of successful treatments.