Historic Venetian Howitzers gradually losing their famous lions

[cannonmn]

I wanted to get some decent photos of the Lions of Saint Mark as cast on the two captured 18th C. howitzers before they are completely gone, or completely unrecognizable, which won't be long at the rate the corrosion is progressing.  They were in essentially undamaged condition when I first inspected them probably around 1980, since they both still had black paint on them at that time.   Paint prevents corrosion since the chemicals which cause the corrosion can't come in contact with the bronze. 

The following set of photos includes some from August 2008 and many from June 2009.  The bottom line is that noticeable degradation has occurred to the now-unpainted lion over only the past 10 months.  This may be more evidence that the corrosion that's occurring here is progressive in nature.  As the surface becomes etched over time, the surface area increases.  That and the accumulation of insoluble corrosion products in the etched areas, acting like a sponge, causes the corrosive acid rain water to remain in contact with the bronze for a longer time after it rains.  You can clearly see these corrosion products, which appear as chalky white areas.

One thing I noticed in the very close-up photos was two distince layers of corrosion, the upper one blue and the lower one green.  I have no idea what this means but it can't be good news.


June 2009:  Trophy No. 12



Below, trophy no. 12, August 2008



Below, trophy no. 12, June 2009.  This lion retains most of its black paint, and I can't see much change over the 10-month period.



June 2009, trophy no. 12.  Following three photos show details of corrosion damage.  Note how black paint simply acts as a resist as used in acid etching.  The areas under the paint are not acted on by the acid, and exposed areas are etched away.







Below, June 2009:  Last photo of trophy no. 12



Below, Trophy no. 14, June 2009





Below, Trophy No. 14, August 2008




Below, August 2008:  Notice in the two photos below how although there's no more paint left on the lion, there's still a relatively smooth, slightly reflective surface on the lion.





Below, June 2009:  Pedestal under one of the howitzers, with sign, showing green stain where copper etched out of the bronze, combined with chemicals in bird droppings and acid rain, is running off with rainwater.



June 2009, trophy no. 14:  The following four photos show how the lion has been etched over the past 10 months.  The surface is no longer smooth and slightly reflective, but very coarse as it is etched more deeply and more metal is removed.









June 2009, trophy no. 14:  The following photos show details of corrosion.  In the first photo, notice how there are two different layers of corrosion.  The higher surface is blueish.  The lower "valley" which is well below the level of the remaining black paint, is more of a green color and is significantly deeper than the blue area.  I have no idea what this means but it can't be anything good.

[cannonmn]

Here's the letter I sent to the Navy:

(personal letterhead)

June 22, 2009
RDML DeLoach (Ret.)
Director, Naval History and Heritage Command
805 Kidder Breese Street SE
Washington Navy Yard, DC
20374-5060

Dear Admiral,

I exchanged letters with the Naval District Washington last year regarding the deterioration of the bronze cannons in Leutze Park, Washington Navy Yard. To quote from NDW letter of 27 August 2008, “we have decided to keep the guns on display outdoors while awaiting professional treatment.” The letter also declined my offer of assistance.

Earlier this month I made a detailed re-examination of each of the bronze cannons in Leutze Park, and recorded my observations on ten short videotapes (enclosed.) I have since put the videos on the “you-tube” website. I noted the continuing corrosion on the cannons, evidence of runoff of corrosion products from the cannons into the ground, and specifically the loss of markings on the cannons. My video at this url: http://www.youtube.com/watch?v=c3OCocX5pU0 clearly shows the disappearance of important markings on one valuable bronze howitzer over a span of only ten months.

I’d like to help the Navy resolve this embarrassing issue. The cannons are dissolving and gradually losing their markings. I’m sure you don’t want to be in the position of allowing continuing damage to these valuable historic objects; as a minimum you are under an obligation to mitigate the damage.

If you would allow me to suggest a simple solution, here it is. The cannons in Leutze Park were once painted black, and when I first inspected and photographed them in 1980, a number retained most of their black paint. Black paint keeps acid rain, bird droppings, and direct sunlight from attacking the bronze. You can see clear evidence of the successful application of black paint to bronze by looking at the small bronze howitzer near the old Commandant’s Office (Reilly’s book, No. 11, pp. 68) which has been kept outdoors in black paint for a long time. There is no evidence of corrosion on the cannon, nor chemical runoff on the concrete mounting.

Extending this method to other cannons would involve carefully removing loose corrosion products, drying the bronze completely inside and out, sealing the vent and bore, applying a suitable primer coat, then a good grade of ordinary black paint. This would protect each cannon for perhaps 20 years, based on my experience using black paint on outdoor cast-iron cannons. Only a removable type of paint should be used, not epoxy paint, so the process is easily reversible in accordance with established conservation practices. I’m not partial to any particular method of conservation, but clearly something needs to be done now.

I’m affiliated with several history-oriented organizations which could potentially assist you with expertise as well as labor. Please let me know if the Navy is willing to accept assistance, which could be provided via the Naval Historical Foundation. Whether any other group steps up or not, I’d much rather be spending time actively helping with this, as opposed to just documenting the issue and complaining about it as I’m doing now.

Sincerely,

xxx


Enclosure:
CD containing 10 video productions regarding condition of cannons in Leutze Park, June 2009.