EDITOR'S NOTE: A park recently asked us for information about the proper procedures and materials to be used in the preservation of 19th-century iron cannon which are used only for display.
A review of Ordnance Manuals and textbooks used at the U.S. Military Academy, West Point, N.Y., shows that from 1859 through 1880 cannon preservation methods did not change. We are certain that research in older manuals would show little change, if any, from about 1808, when the artillery service began to be equipped primarily with iron cannon, through the era when bronze was adopted for certain field guns (1836 to 1865).
We thought we would share the information with readers.
Iron guns were painted on the outside with a waterproof "lacker" (sic) after all rust was removed. The vent and the bore were coated with an oil/tallow/beeswax "grease" which was renewed once a year. The lacker was subject to periodic inspection and renewed as necessary, depending on weather and storage conditions.
While the manuals provide complete formulas for both the "lacker" and the "grease," for preservation purposes today, there are much better, modern paints and moisture-replacing "grease" available.
We suggest thoroughly cleaning the exterior and interior with bronze wire brushes, by hand. Ordinarily, light sand blasting of Civil War-era iron Parrott Rifles and U.S. 3-Inch Wrought Iron Rifles (Ordnance Rifles) doesn't result in any visible damage.
However, bronze guns should never be sand blasted, nor should the exterior of a rare piece. One might consider sand or glass-bead blasting of the bore interior to ensure thorough cleaning, if the intention is preservation with no plans to fire the cannon.
After the surface has been cleaned, it should be primed with a modern spray-applied, self-etching automotive primer, two coats. Next, you should apply two light coats of a high-quality automotive lacquer of 1990s-era formula. (Automotive paint has undergone four major changes since the 1930s.)
Any place where original markings appear on the cannon should be approached with great care so as to protect, but not fill in, the stampings.
As for the bore and vent, once you are satisfied they are clean, we suggest a heavy application of "Ballistol" multi-purpose lubricant. This is a bio-degradable, non-toxic food machinery lubricant that has proven its value in protection of artillery pieces and machinery in both World Wars and since. (It is available from Washington Trading Company at 800-253-2460.)
You would apply this using a made-up tool similar to a tight-fitting original sponge-rammer.
After a thorough soaking with Ballistol (a couple of days for it to seep into the pores), we would suggest you look for a high-quality waterproof grease and coat the bore and vent with a thin layer.
A very good oil to use, which is now used by the military, is sold under the name "Break Free" and is available at most hardware, automotive or gun shops. We do not recommend a light-weight oil such as WD-40 which is not long-lasting in a situation like this.
As an additional step, after the vent is treated in the same fashion as the bore. we suggest that you plug the vent with a 1/4-inch of glass-wool insulation, about 1-inch down from the surface, then fill up that last inch with a plug of pure plumbers' lead. This will seal the vent against moisture as well as bugs, wasps and children. The lead can easily be removed if necessary at a later date.
Caution: Any oil or moisture should first be eliminated from this vent area by heating with a propane torch. Although the quantity is small, hot lead coming in contact with a liquid will cause an explosive-like splattering. Whoever does this work should take precautions of wearing leather gloves, a long shirt and eye protection.
If you keep the cannon in a slightly muzzle-down position as suggested in the manuals, and renew the coating of Break-Free or other moisture-displacing lubricant, at least once a year, you should have no further deterioration problems.
If for any reason you wish to remove the lubricant protecting the bore, all you have to do is thoroughly wash it out using denatured alcohol as a solvent. The alcohol makes quick work of cleaning out the oil.