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What’s in the tank?

By Deanna de Boer
STOF THPO Collections Assistant

Not many people think about what happens to artifacts once they’re taken out of the ground. Often, they can’t just be put in a box on the shelf, and need a little TLC to make sure they are stable enough to be placed in the vault.

For iron objects, without stabilization they can become brittle, and split or flake. If the object is very degraded or corroded, the iron core can fracture over time.

In 1855 Fort Shackelford, a U.S. Army Fort on Big Cypress was burned to the ground by the Seminoles. The STOF THPO spent many years searching for the fort site, through researching oral histories, metal detecting, and archaeological excavation.

Collections Assistant Deanna de Boer examines a square nail in the electrolysis set up. (Photo Sam Wade)

In the winter of 2017 a line of posts, hand-cut square shaped nails, and additional remnants of the old fort structure were found. Since then two field seasons of excavation, with the help of students at the Afachkee School, have uncovered dozens of artifacts. The majority of these have been metal.

For a lot of the iron objects found at the Big Cypress Fort Shackelford site, once excavated, they started to degrade. Now that we have the objects back in the lab, we have struggled with how to answer the question; how do we take care of these objects?

It was important to us in the THPO Collections section that whatever we did to help preserve the objects to be inexpensive, reproducible, and effective. We wanted to be able to do it over and over again for a lot of our iron objects, like the ones from Fort Shackelford.

Square nail and nail head suspended in the tank, with corrosion on base. (Photo Sam Wade)

After some research and consultation with the Ah-Tah-Thi-Ki Museum Conservator Robin Croskery Howard, we settled on a simple electrolysis set up. For about $200, we bought a simple 60v Battery, a waterproof reptile tank, wire mesh, alligator clips, sodium carbonate, and a metal hang bar.

The artifacts we wanted to conserve would be suspended in a solution of sodium carbonate and distilled water in the reptile tank, and basically hooked up to the battery.

An electric current would be run through the object at low voltage and amperage. This process does a couple things. One, it allows the iron core to stabilize and become stronger.

Secondly, tiny bubbles form through a chemical reaction, and the corrosion begins to slough off the artifact. Once complete, the objects are removed from the tank corrosion free!

Electrolysis tank set up at the end of the first run of artifacts. (Photo Sam Wade)

Unfortunately, to make sure there isn’t damage to the artifacts the process is very slow and can take weeks or months depending on the size of the artifact.

So far, we have been able to work on two objects in our little electrolysis set up, with big plans for the future. We have placed in one square nail and one piece of cast iron from Fort Shackelford.

Both the nail and the cast iron piece have responded very well to the treatment, and after being taken out are visibly free of corrosion.

After they are removed from the tank, they are additionally sealed with tannic acid and wax to make sure they are as protected as possible.

This fall, we hope to continue the process and work on more objects from Fort Shackelford and other sites. Hopefully, with a little help from a battery and a reptile tank, we will be able to preserve these objects so they can continue to help tell the Seminole story for years to come!