Conservation Highlights: Get the Lead Out

Tuesday, May 15, 2018
Conservation Hightlights
Author: 
Karen Martindale, QAR Conservator

The most common material conservators encounter from the site of Queen Anne’s Revenge is lead. In fact, with a total of more than 200,000 (and counting!), the most prevalent artifact from the site is lead shot. Conservators also find more unique artifacts made with lead, such as patches to repair the ship, cannon aprons, tacks, game pieces—even the ship’s toilet!

Lead is one of the most stable metals found on archaeological sites. Although it is a soft metal that can be melted, bent, or scratched easily, it does not oxidize quickly, like we see in wrought iron from the site. This is because, on the atomic level, it has an equal number of protons and electrons, and the electron shells are all full, meaning a great deal of energy would be needed to destabilize it and cause it to corrode.

With so many artifacts made of lead, the conservation process is relatively straightforward, with the major concern being that the softness of the lead means that it is easily damaged by our tools.  If there is a thick layer of concretion on the artifact, conservators use air scribes to remove it, like we would to break down a concretion. If the concretion layer is very thin, conservators instead use a dilute solution of hydrochloric acid to dissolve the concretion layer and use brushes or dental picks to remove the remainder of the concretion. Once the concretion has been removed, the lead can be dried, and is ready for display.

Image:
-Lead shot from the QAR site. Image by NC Department of Natural and Cultural Resources.
-Game piece from the QAR site. Image by NC Department of Natural and Cultural Resources.
-Lead tacks from the QAR site. Images by NC Department of Natural and Cultural Resources.