As mentioned in Dave’s blog of Nov 22nd, our whole department got to play with hammers, chisels and other air-scribes while on the engine this week. The feeling that conservation is somehow (or sometimes?) close to mining was strongly emphasized by having on average of eight people confined in a tank, hammering from 9am to 5pm. The analogy stops there though: we’re not underground AND, in front of our wide-open eyes (behind our dirty protection glasses), the Monitor’s engine takes shape and becomes alive!
Approximately 2 tons of concretion was removed from the beast, i.e. about 500 lb/person removed in 4 days (who needs to go the YMCA?).
So below is how it looked Monday morning and under that is how it looks today:
The conservation state of the metal is heterogeneous. Copper alloys elements are of course in great condition but iron alloys are soft, flaky, sometimes totally gone and their original shapes were only kept as voids in the concretions (this is the case of the dogbone in wrought iron for example). The reversing gear mechanism is getting cleaner but suffered a lot of preferential corrosion since it is a mix of copper and iron alloys. The cast iron steam chests have gorgeous surfaces but great care must be taken when working around it because corrosion has resulted in graphitization of the superficial layers making it soft.
Conservators accessed the interior of the port side of the engine cylinder and solution coming out of it was sampled for chloride analysis. While some of the sample was unavoidably mixed with city water, the chloride level reached 118 parts-per-million. This is very high considering our city water chloride levels vary from 15-22 parts-per-million.
Other neat small finds were a tiny wood board (beautifully preserved), turtle bones, a rivet, and a tool made of wrought iron with a wood handle (either a file or a wrench).
“Hammer fest” continues next week so stay tuned and don’t hesitate to make comments or ask questions – we’ll be happy to answer them!
Have a wonderful winter weekend!