Conservation

Alexandria Ship Project

About

Conservation

For over 200 hundred years the remains of the Alexandria ship lay beneath the silt and fill along the Potomac River. During that time, water penetrated deep into the cellular structure of the wood and bacteria began to eat away at the cell walls, creating microscopic perforations. Water filled these perforated voids and now has become part of the wood structure. Before scientists can reconstruct and install the ship in an exhibit the water must be removed, but it must be accomplished in a manner that regulates the water removal or the wood could severely distort, shrink, cup, twist and split, impeding the chances of a successful reconstruction.

The stabilization of the timbers will begin following completion of laser scanning and timber recording. The 3-D and 1:1 computer drawings generated from this data collection will be combined with chemical and physical analysis of the wood's macro and microstructures to help determine the extent of deterioration and allow for the development of specific protocols to manage the timbers.

Before the water can be removed and the timber dried, iron that has permeated into the wood will have to be chelated, or drawn out, by soaking the wood in several solutions of ammonium citrate. Iron was used to assist in fastening the planks to the framing as well as hold the framing together but as the fastening corroded the corrosion products penetrated the wood. If the iron is not neutralized and removed from the timber it is possible that pyrite (FeS2) could form deep under the surface and oxidation of the pyrite over time will most likely severely damage the wood.

Chelation will require about a year to a year and a half to complete, but once this potential issue has been mitigated, the wood will have been prepared for the next phase, dehydration of the water. To undertake the dehydration, a two-part pre-treatment of polyethylene glycol is planned, which will displace a percentage of the water, bulk the cellular structure and provide the wood with some added mechanical strength before gently removing any remaining water by vacuum freeze-drying. After freeze-drying the wood will receive a final surface cleaning and broken timbers will be prepared.