How do you learn proper conservation techniques? It all began with a class in Museum Studies at East Carolina University. Two of us were also taking a conservation class at the same time and one of us had already had it. Well, the fact that you've had a class does not make you a proper expert, as we later found out. Experience in the field was an absolutely necessary ingredient. None of us had that. In other words, we had to start from scratch and gain that experience. A little life experience was a plus as well. What's worse is that every "expert" in the field gave us different advice, some of it quite detailed for such an imperfect, resource-challenged project. There's a big difference between the ideal and the practical, although you should always be guided by the ideal. I used to manufacture and install stained glass windows, which on occasion required me to adapt to new situations that I might encounter in the field. It happened almost on every job. Likewise, most conservation projects necessarily center upon the practical; compromise must be a familiar idea to us all. This is a delicate balance, affected by resources, time, location, future storage capabilities... a plethora of factors.
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| Me back in the good old days (before the grey crept down my face), soldering my stained glass window to metal hangers that I had to adapt to the masonry work of this church in order to hold my window in place. I had always worked on wood before. This was new. The window had to be fitted closely to the masonry in order to seal it properly. This window required three months of drawing, cutting, painting, firing, and assembly. I wasn't about to let it come out of that wall! |
One really wild idea that was told to us was to put as many as fifty coats of expensive tannic acid solution on the Brooke Cannon Shells that we worked with, even though the cannon from the QAR got only three. Well, that was a sheer disaster; shall I say "Dismal Failure?" Imagine 50 coats of red Krylon on your Red Ryder... or 50 coats on anything with great detail... where was that picture of the British carriage again? lol All diagnostic features disappeared in a sea of uneven paint! It was gross... except at a distance, when you couldn't make out the details of the wreck. Not only was it thick, but the metal never reacted to it. I remember seeing a beautiful old Mustang one time and, as I approached, it became obvious that something drastic had happened to it. That's what we had with SLM-006, the only Mullane shell contained in the Neuse artifact collection. It's a special piece for them. Ideally, this shell needs to be completely redone, this time with 1/10th of the expensive chemicals and a healthy application of common sense.
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| Examples of corroded artifacts: SLB-003, EH-003, and GC-002 |
Then came the idea of mixing phosphoric acid into the tannic solution directly instead of making a dilute solution first and using a medicine dropper to adjust the pH that way. I should say that that was not the fault of any trained expert, but the results of inexperience in laboratory methods. Again, this is why you need a supervisor for such projects (which we lacked, unfortunately); but fear not, the more attentive of us were able to persevere through the rough areas and make a proper go of it. The best method for adjusting pH comes from Algonquin College's video (in case you're interested). By the way, adjusting the pH is apparently not as critical as some might lead you to believe. J.T. Baker makes a tannic acid that should already be the proper pH. Still, the other tannic acids available do not get much higher in pH and effect the results in no observable way. Another oft quoted detail that seems to make little difference, but can be used to make a little political noise. The mistake with the phosphoric acid just wasted our time and made the artifacts quite ugly. You can see the results of the phosphoric acid on the shells in the last of these three comparison photos (SLB-002 from the start of the day 4/25/2012):
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| The first image is how the objects looked when they were conserved before, with Conquest, a tannic acid and acrylic mix. The second picture is the same object with most of the Conquest still on it, but with the oxidation scrubbed off. Forty coats of tannic acid solution were added on top of the Conquest. Bare metal still shows through these many coats, having never reacted with the metal. The last image shows a similar shell treated correctly, with only three coats of tannic acid (like the cannon at the QAR lab), and powdered art-quality graphite stippled into resistive areas to make the black color uniform throughout. Most experts will agree that excessive coats are not necessary. As you can see here, they are quite terrible in appearance by comparison to the proper method. Note that the first and last images show similar textures on the artifact. Diagnostic details are preserved. |
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| One example of phosphoric acid overdose. The image to the left is a whitish brown because of the phosphates covering it and unreacted tannic acid on top of that. It should be noted the phosphoric acid is sometimes used for the same purpose as tannic acid to preserve iron and that an a cream-colored coating would not harm the iron and protect it just the same, but what an ugly result! The image on right is a properly-reacted SLB-002 with tannic acid. Again, diagnostic detail has not been lost. |
Perhaps the biggest help was a minor reference to the "stiff" bristle brush that did not sound much like a paint brush, which was the assumption for so long, an uneducated method that I was to discover that was employed by a former group that was later fired for the same thing. The tannic acid had not been getting into and reacting with the metal because we were painting it on like the red paint on that old metal shed that my father had taught me how to paint on... kind of like Mr. Miagi with that "brush up, brush down" bit. A sea of tannic acid just sat there like a light beige clear overcoat. When there are iron oxides present, like on a freshly electrolyzed cannon at the QAR lab (see pic), the tannic will react easily with those to turn black, even when painted on. That's just not what we had nor what should be done in any situation.
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| Cannon from the QAR fresh from the electrolyte solution. It's ready to be scrubbed down in tannic acid. This will instantly turn the rust a dark purple hue, give off a lot of heat (exothermic), then turn deep blue-black. The QAR lab only uses three applications of tannic acid to accomplish this. |
There was hope! A very old paper by J. B. Pelikan in 1966 was the first to show a picture of a "stiff" bristle brush in use with tannic acid and this picture verified what I was beginning to think, but which none of the modern literature would say directly. After 1966, it would seem that everyone in the field just began to assume that's what you use and called it simply a "brush" from then on:
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| Conservation of an iron knocker on the door of the state castle Hradek near Nechanice. The surface of the fittings and the decorative nails is being thoroughly brushed with a tannin solution. (Pelikan, 1966:113) |
This technique works on bare metal as well as rusty iron. Again, after 1966, some of the literature hinted at that, but never came right out and said it! It's those little hints, lost and forgotten in an academic sea of "paper-plexion" that have to guide you sometimes. Again, the education is helpful... as long as you use some practical sense and real-life experience to temper it with. Thank you Pelikan!
I can only speak for myself and, needless to say, I learned conservation in the field as much as I did in the classroom... and in the literature! I mean, I had a few years of laboratory (and a lot of practical... I'm older, after all) experience, but very little in conservation. Some of the experts were of tremendous help, too. My conservation instructor, Shanna Daniels, contributed valuable assistance to us along the way. Also, the Queen Anne's Revenge (QAR) conservator, Wendy Welsh, was of the utmost assistance in the last few weeks. By the way, Wendy will be coming to a symposium on the conservation of the CSS Neuse at the Neuse Regional Library at 510 North Queen Street in Kinston on May 19th at 2:00 pm. Leslie Bright, the original conservator from the 1960s will be there as well. This will be very informative and I know that I have my questions! Don't forget to hit Bathfest earlier that day in Bath!
Another conservator who has been hugely helpful is Nathan Henry of the Underwater Archaeology Branch (UAB) at Ft. Fisher. Henry deals mostly with salt-infested marine artifacts, but his practical knowledge of metals conservation was quite valuable. The UAB also has 73 folders of negatives and documents from CSS Neuse's original conservation in the 60s & 70s. Digitizing those would be hugely valuable to the festivities this summer and the new facility with its new exhibits, which could use some of those pics. Scanning those is what I did last week. UAB was planning to digitize their shipwreck files this summer and I gave them a head start on the Neuse files.
Last but not least was our faithful Admiral of the High Seas, Dr. Brad Rodgers, the director of Maritime Studies at ECU. His manual, The Archaeologist's Manual for Conservation: A Guide to Non-Toxic, Minimal Intervention Artifact Stabilization, published in 2003, gave us valuable insight into the methods.
The best part of this project was the problem-solving. The artifacts that we worked on were several cast iron Brooke and one Mullane shell, a wrought iron trunnion cover (cannon carriage piece), a flag pole socket and three wrought-iron eyehooks. Try as we might, the wrought iron pieces did not take the tannic acid solution very well. However, with Shanna, Wendy, Brad's, and Nathan's help, we were able to find the right formula/technique and get excellent results (almost surprisingly instant results), at least on the cast iron... finally! Still the wrought iron artifacts can easily be coated with tannic acid and then charcoal, using the coloration idea behind Conquest, but without the vinyl, fine sand, and acrylic coating that has shown possible galvanic corrosion problems. These are minor, but avoiding them is easy with this method.
I could also point out another flirtation with the literature at the end of this process and which got misconstrued and confused once again. There is some evidence that graphite could have a galvanic corrosive effect with cast iron under the right conditions. Ahem! :) However, in order for an electrochemical process such as this to take place, the graphite and iron would have to come into direct contact AND they would have to be able to conduct a current. Powdered graphite (I actually used artist-quality charcoal which is a different allotrope of carbon from "graphitized iron") suspended in dried tannic acid could never conduct electrons because the particles of graphite cannot actually touch one another... the "wires" aren't connected. Now, if you're talking about solid graphite rods (pencil lead, for instance) laying directly against bare metal, that's a different story. This was just another red herring... something to stall progress. Still, a valid concern, however minor and distracting, and it deserved some thought. To appease the theoretical alarmists, a simple coat of Acryloid B-72 (basically, a lacquer) over the area to be stippled with graphite solves that little problem right away! It even makes it easier to do because the older layers are not dissolved by the new application. NOTE: Still, I performed an experiment to illustrate that the graphite/tannic acid mixture does not conduct a current when dry and, therefore, is harmless. The artifact looks beautifully uniform throughout and will last a long time in the proper care without any galvanic problems other than what was already there in the larger, more serious and irreparable problems between the copper alloy and the iron.
This is the major galvanic concern, especially if water is still trapped inside the shells to act as an electrolyte and complete the circuit! The differing metals cannot be removed from one another without damaging the artifact and must be somehow made electrically inert through temperature and humidity controls upon display... and by popping the hood and draining the excess fluids! lol Again, this is the REAL galvanic problem.... My, where is the time going!? :)
Dr. Brad Rodgers, with 25 years of experience in the field, stated that metals were predictable. He should know, I guess. There is no need in reinventing the wheel. In other words, it's not that hard, folks!
All of this effort was excruciatingly intense and complex because of the differing and often conflicting opinions and variability of lab practices (remember that these are not usually chemistry majors). One piece of advice for those getting into the field... you will be surrounded by people who only half understand the methods, have minor lab skills or experience, or, worst still, have been mis-taught or misled in some way. Don't dispute them. They can always find someone with credentials to back them up on any tangent they can dream up. They can make your life a living hell! Get all of the information you can BEFORE you start, make a plan, and then get the job done. Most of all, get it done and done right.
After all that happened, after four long, difficult months, after all the starting, stopping, and testing suggested methods (most of which did NOT work) along the way, success came at last. Needless to say, I got an "A" in conservation class! It took perseverance and a lot of common sense, too. Loads of common sense... please, never underrate common sense! You can tell that I'm ready for a break, huh?
British author, Douglas Adams said, "
After all that, I could finally say, "Call me conservator!" Maybe someday, I will have the chance to work on other projects. But, for now, I just wanna kick back and have a beer! You know how fond I am of Spaten Oktoberfest... :)
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| In this picture, there are three shells visible, the trunnion cover in the background and the eyehooks in foreground. One note is that Jack Bell (Bell, 2003:32 and 113) states in his book on Civil War ordnance, Civil War Heavy Explosive Ordnance: A Guide to Large Artillery Projectiles, Torpedoes, and Mines that while all sabots from Union ordnance were listed in contemporary sources as “brass,” all Confederate ones were listed as “copper.” Still, he states that “Some of the Confederate ones may actually be brass or some alloy other than pure copper….” (Bell, 32). As observed on April 9, 2012 and obvious in this picture from April 25th, the brass appearance on the sabots was due to the protective coating applied in the 1970s. The contemporary sources were correct in that a high-copper content was used, as you can see on the standing shell to the right. |
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| GC-002, the trunnion cover, after proper conservation |
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A full gun crew works a 9" Dahlgren, USS Mendota. Note the trunnion cover in the center of this photo. It kept the cannon from jumping off the carriage when it fired. Brooke guns were mounted on a carriage that was steeper in angle on the front, providing for two angles on GC-002 above. |
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| NE-3W-9, an eye hook that we named EH-002, from 1975 to the present. |
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| Eyehooks of wrought iron and coated in tannic acid with graphite added for color. |
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| A display idea showing an extension of the fuse and its components extended from the hole from which they fit. The angle of the display will show off the entire structure of the shell. |
Update from May 19, 2012 and the "Wood, Iron, and Time" event where we got to speak with Leslie Bright and Wendy Welsh in Kinston:
Leslie told us about the details of the conservation process that he helped to pioneer and Wendy talked us some of the modern techniques that we use today. I was also able to talk with Spencer Waldron, retired conservator for Historic Sites. According to Spence, Leslie loved the Conquest, which he said was properly applied by scrubbing it in (another late, but welcome reference). Apparently, Leslie used Conquest up until the time he was rushed by the state and he used Epoxy Resin to finish the shells. This was not so easily apparent from his book. I thought that I had seen some evidence of this in the shells we had. I remember having to argue this point as well. I'm thinking that conservation is a touchy subject for some folks. But, not so for Leslie and Wendy. This was an enjoyable and friendly event! It was nice to sit in a room with all of these minds: David Moore was there, Morris Bass, the site director and a most knowledgeable scholar in his own right, his right hand, Holly Weaver, Bright & Welsh, of course, and Bill Rowland, a man who worked tirelessly to record the early recovery efforts and draw plans, locate GPS coordinates, etc. There was another retired scholar and I wish I could remember his name.
As it turns out, Spence told me that the site hired some extra hands after the storm in 1999 that painted the Conquest on like I described earlier instead of scrubbing it in... they were fired for wasting chemicals and time. I guess you can't fire volunteers... lol.
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| Leslie Bright in Kinston, May 19, 2012 |
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| Wendy Welsh in Kinston, May 19, 2012 |
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