Last month, we were able to complete one of the last major steps in the conservation of USS Monitor’s two XI-Inch Dahlgren shell guns: boring concretion out of the barrels. Material Culture Specialist Hannah recently showed off what we found in this process (coal is, indeed, cool), but why clean the gun bores to begin with? And how do you actually go about doing that, anyway?
The ‘why’ has a few pieces to it. There are benefits to our archaeological knowledge of the wreck, but our primary concern was keeping the guns in good condition. Monitor’s guns are made of iron, and specifically are made of grey cast iron. Grey cast iron is not 100% pure iron; it contains about 4% carbon, and that carbon exists as flakes of graphite locked in by the metal surrounding it – picture little shavings of pencil lead and you won’t be that far off.