Plastics in Our Collections: Chapter 1

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Collecting latex from a tree
© User:Iamshibukc / Wikimedia Commons / CC-BY-SA-3.0

The Plastics Age

History is filled with ages that are tied to the innovation of materials:  The Stone Age, The Bronze Age, and The Iron Age. We are currently in The Plastics Age. Plastics have changed so much in our daily lives. Plastics are around us all the time.  They are in every electrical thing in our houses, in the clothes that we wear, in our furniture and the packaging of our food.

This means that as caretakers of historic objects, museums have to consider how long plastic materials will last in our collections. We focus on what we have to do and learn in order to care for plastic objects. We also study plastics in order to store them in ways that better ensure their survival. This is a complicated thing.  Plastics are not simple materials, and what works for one may damage another.  Some plastics have been around longer than others, so we know more about them. We can see how they’ve aged. For other plastics, we can guess at how they will survive (or not) based on their behaviors and chemistries, while still others are a gigantic question mark.   Read more

Coal is cool: archaeological implications of Monitor’s cannon boring project

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The archaeological conservators boring one of the two Dahlgren guns. 

The Conservation team recently bored USS Monitor’s 2 XI-inch Dahlgren cannons. This was a huge step in the objects’ treatment. It came from a need, but also required the right expertise, a TON of planning, donor funding, and specially crafted parts to make it happen. This task was completed for absolutely no archaeological reason. It needed to happen to conserve the artifacts and, therefore, it happened, but that doesn’t mean that archaeological interpretation didn’t benefit from the project.

So, here is my tale of why coal is cool…

To accomplish “archaeological investigation” of the concretions which came out of the guns’ bores, we set up a screening station at which the screeners – me, and the poor fools I tricked into helping me (our CEO Howard, our intern Christy, and our volunteer Heidi) – broke up the concretion into smaller bits of concretion until it fit through the screen and we could say with fair certainty that there were no artifacts left inside. This is a standard archaeological practice called sifting. What is maybe unique about our situation, is that since everything belongs to NOAA, we don’t get rid of the dirt and rock after its sifted, we bury it and save it in case there are techniques that it will be useful for in the future. No, I won’t tell you where we bury it. Actually, even I don’t know where, so I couldn’t tell you if I wanted to.   Read more

The Bronze Door Society Saves the Day!

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It was going so well, until it wasn’t. . .

It was a crisp winter morning, the year newly minted as it was only January 2nd.  I had just finished preparing all of our samples to run on our old, but usually reliable, ion chromatography (IC) unit.  (Aside: The IC is vital in measuring when the desalination treatments of USS Monitor objects are complete.)

Our IC unit ran out of preventive maintenance coverage (read warranty) as of January 1st.  The IC is so old that parts are hard to find and we couldn’t buy a new preventive maintenance policy on it.  Our IC was balancing on the precipice of obsolescence and inactivity.   Read more

Another day, another Dahlgren!

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Cutaway side view from the patent drawing for Dahlgren Shell Guns, 1861

Today’s question seems like a simple one – how long is a Dahlgren Shell Gun? As I mentioned previously, I am designing a set of drilling equipment to clean inside the XI-Inch Dahlgrens recovered from USS Monitor, and as part of that I need to establish parameters for actually using the drilling equipment. Well, one very important parameter to know is how far in can you drill? There are two ways to answer that question: you either need to know exactly how deep the bore is before you begin, or you keep pushing the drill into the gun until it hits metal. Given that the latter option cuts a shiny new groove into the back of the bore, I like to aim for the former.

Fortunately, guns from the 19th century often have government ordnance records or patent drawings which give more or less complete dimensions, and Dahlgren shell guns in particular have both patent drawings and multiple Board of Ordnance drawings which survive. Unfortunately, they don’t all match. The patent drawing gives a standard ratio for all Dahlgren shell guns that the bore should be 12 calibers in length, meaning an XI-Inch gun should have a bore 132” in length. The Board of Ordnance drawings give a bore length of 131.2” for an XI-Inch Dahlgren, or approximately 11.93 calibers. In addition, we have both Board of Ordnance pattern drawings and inspection drawings, and while the bore lengths are the same between them, the powder chambers have different measurements.   Read more