Removing encrustation is only the beginning of conservation. Objects that have lain in seawater for centuries are saturated with chlorides. Unless those chlorides are driven out of the object, it will crumble to pieces. Depending on the artifact, that process of can take years or only hours. There are various techniques for driving out these chlorides, and archaeological conservators have spent decades developing better methods. Ships of Discovery’s conservation laboratory was dedicated to improving methods of conservation for a variety of artifact materials.
Conservation of Iron
Electrolysis is the standard conservation treatment for iron artifacts recovered from salt water. The idea is to drive out the chlorides (salts) that have penetrated the metal.
We were surprised to learn when we researched the literature that despite decades of using this method, no one had determined the optimal current density for the electrolytic reduction of iron artifacts. So we decided to do some current density experiments and figure it out.
What we learned was that the old ideas were completely wrong!
Read More About It
Worth Carlin, Donald H. Keith, and Juan Rodriguez. 2001. Less is More: Measure of Chloride Removal Rate from Wrought Iron Artifacts During Electrolysis. .
Conservation of Waterlogged Wood
As odd as it may sound, sugar is good for conserving waterlogged wood. It helps support the wood’s cellular structure, which has collapsed during centuries of immersion. We have developed a method to better maintain a constant concentration of sucrose to impregnate wood, giving artifact conservators more predictable results using a small tank and pump. 
While sugar provides cell support for the wood, it also provides nourishment for organisms we do not want growing in our treatment tanks or on our conserved artifacts. Rohm and Haas Company (now Dow Chemical) generously donated a supply of Kathon CG/ICP to add to the sugar solution to prevent unwanted fungi, algae, bacteria, and slime from colonizing our lab and museum displays.
The proof of concept was tested and confirmed with the successful conservation of a 1000-year-old Lucayan canoe paddle found on Grand Turk island. It is presently on display in the Turks & Caicos National Museum.
Read More About It
Donald H. Keith. 2012. Nothing Short of Miraculous: The Saga of the North Creek Paddle. Times of the Islands, Fall: 56-61.
Improved Corrosion Inhibitor for Ferrous Artifacts
What do treating your dog for fleas and conserving a 2-ton iron cannon have in common? The need to increase post-conservation treatment penetration. After more than 20 years of being on display and in storage at the Corpus Christi Museum, the microcrystalline wax treatment was thin and no longer impermeable.
Our lab has developed an additive for tannic acid treatment to achieve better penetration and long term protection. We do not use it on our pets, though.
Read More About It
Worth Carlin and Donald H. Keith. 1996. An Improved Tannin Based Corrosion Inhibitor Coating System for Ferrous Artifacts. International Journal of Nautical Archaeology, 21 no. 1:38-45.
Electrolytic Treatment of Pewter
Pewter recovered from marine sites is difficult to treat because it is an alloy of two metals that react quite differently to the salt water environment. The higher the quality of the pewter—that is, the less lead it contains—the more difficult it is to treat.Through tightly controlled experiments, our lab has refined the technique of electrolytic reduction conservation treatment for pewter.
Read More About It
Worth Carlin and Donald H. Keith. 2007. On the Treatment of Pewter Plates from the Wreck of La Belle, 1686. International Journal of Nautical Archaeology, 26 no. 1:65-75.
Galvanic Removal of Metallic Wrought Iron from Marine Encrustations
Historic shipwrecks frequently contain a large proportion of wrought-iron tools, fasteners, and other types of artifacts. Encrustations readily form around such objects in many marine environments. Depending on a variety of factors, the iron objects inside these encrustations may be well preserved, completely disintegrated, or poorly preserved but still present. The latter type of encrustation is every conservator’s nightmare because removing the encrustation yields merely a poorly preserved artifact still in need of extensive additional conservation.
Neatly separating the artifact from its encrustation in order to obtain a natural mold for casting is generally impossible. Having encountered this problem many times, we began to experiment with the extraction of metallic iron from poorly preserved encrusted artifacts using galvanic dissolution. Data on rates of dissolution were gathered for three experimental configurations. The results of a test conducted on an encrusted artifact were promising, but inconclusive.
Read More About It
Worth Carlin, Donald H. Keith, Juan Rodriguez. 2002. Galvanic Removal of Metallic Wrought Iron from Marine Encrustations. · October 2002
High Differential Chloride Removal
A huge amount of fresh water and chemicals are consumed by the electrolytic treatment of artifacts. Our conservation lab addressed this problem by developing a technique to extract chlorides from used electrolyte using Amberlite ion exchange resin donated by Rhom and Hass Company (now Dow Chemical). The system takes advantage of the concept of recycling. The proof of concept testing in our laboratory meant that the liquid could be reused saving both money and resources.
