Cannonmn, as it was described to me, the guns are under the stewardship of the Deprtment of the Navy - Naval Historical Center in the name and representation of us all. I was tempted to tell the man that in that case I would be on my way to the Washington Navy Yard posthaste, to collect one of my Venetian 5.75'' howitzers because I'd really love to peruse it up close and at my leisure but I just didn't have the stones.
I talked to Mr. Kim Nielsen, who is the Director of the U.S. Navy Museum in D.C. and he was an extremely gracious gentleman, I seriously think that if I had wanted to talk for an hour and a half he would have done so. Anyway, let me preface this by saying Mr. Nielsen is the head of the museum he is not a conservator or a bronze specialist although he has had classes in both these fields. His opinion (and the opinion of the museum's curator) is that the surface condition of these guns is not what should properly be called bronze disease. He's of the opinion that the guns conditions are what he called natural bronze oxidation albeit oxidation combined with and aggravated by the air pollution and acidic rain that are present in any urban environment. He referred to the surface of the barrels as a patina and he further stated (and this was news to me) that scientific research in this area has not reached any final conclusions, that there is a train of thought that this patina should not be altered in any way because it might actually be acting like a protective barrier preventing any deeper corrosion of the metal. This last part of the preceding sentence was in response to my mentioning the Spanish guns at the Presidio, his comment on this was that protective wax coatings may be put on these guns for specific reasons, like to protect them from sea salt in the air.
The museum has a Dahlgren bronze boat howitzer that was kept outside, now being studied by conservators to try and answer some of these very questions raised by Mr. Nielsen. Some years back, one of the bronze guns from Leutze Park was also removed to a lab to be studied and then treated, you can read the steps they took on this Spanish 12 PDR named El Alano at the site below.
http://www.history.navy.mil/cannons/cannons57.htmIf you read this article you'll find that some of the things that are stated seem to contradict some of the things that Mr. Nielsen proclaimed, he also told me that he doesn't think this barrel has yet to be returned to the park even though the article says it was scheduled to be returned in 2001. John, another interesting aside that was told to me is that when these tubes get the full conservation treatment they have a tendency to turn a brown color, which might explain the deep color of that barrel you commented on at the Presidio. Mr. Nielsen mentioned that a lot of people, including many conservators would prefer to keep the green patina. I'll mention one last thing that isn't very pleasant to hear; Mr. Nielsen told me there is one very simple way to stop any further deterioration and that is to get the barrels indoors in a protected environment, unfortunately he also said there is no space available in any Navy museum. If the experts ever decide this should be done the cannons would all be taken to a Navy storage wharehouse in Virginia where the public would have no access to them.
I was told that the person that is directly responsible for the conservation of the bronze guns of Leutze Park is Mr. Mark Wertheimer, he is the Armory Supervisor and acting head of the Naval Historical Center's Curator Branch. The phone number is 202-433-2318.
I think you should be the one to speak to him, you saw and felt these guns with your own eyes and hands and you know more about bronze disease than I do.
PS You may find this amusing; near the very beginning of my conversation with Mr. Nielsen I of course brought up the bronze guns of LUTZ park and he didn't even laugh at me. Good luck
