By Ashley Ramsey Hannum, Archaeology Lab Assistant
Have you been wondering if we would ever finish treatment on Captain Kidd’s cannon? You certainly wouldn’t be alone. Cannon #4 from Kidd’s Quedagh Merchant, which sank off the coast of the Domincan Republic in 1699, has been undergoing conservation treatment in the National Geographic Treasures of the Earth exhibit since 2011. The lengthy treatment, called electrolytic reduction, helps remove all of the salts that the cannon absorbed from 300 years in ocean water. The process also helps remove the thick layer of minerals and concretion that built up over that time.
After years of conservation, the cannon is finally ready for the last stages of treatment. The first—and most challenging—step is boiling the cannon in highly purified water. The boiling water creates tiny bubbles inside the pores of the iron, helping to remove the final amounts of salt and minerals.
You may be thinking, how does one boil a 1,500 pound, over 6 foot long piece of iron? Since we certainly don’t have a stove that big, we had to get creative. The Museum’s awesome facilities team had the idea to divert steam from one of the building’s giant boilers, typically used to heat the museum, through the water in the cannon’s tank. Theoretically, the heat from the steam should bring the water to a boil.
We placed the cannon in an 8 foot long, galvanized steel water trough, designed for holding water for livestock. Steve, our HVAC extraordinaire, created some custom copper pipes, which brought steam from the boiler through the water. The steam took quite a long time to heat the water. Imagine how long it takes to boil about a gallon of water to make spaghetti. Well, we needed to boil 220 gallons of water to cover the cannon. It took almost 7 hours to bring it to a boil!
After a couple weeks of intermittent boiling, all of the last salts were successfully extracted. The cannon is now soaking in an alcohol bath to dehydrate it without exposure to air. Once all of the water has been removed, it will be ready for its final coating and sealants. The cannon can then be safely stored in air without risk of rapid deterioration.
New shipwrecked artifacts are now installed in the exhibit, and the process begins all over again!
Treasures of the Earth gallery manager, Josh Estes, visits Captain Kidd's cannon.
Conservator Christy O'Grady shares the cannon with visitors in the Wet Lab.
Christy and Ashley carry out final steps in the cannon's conservation treatment.