Hey CannonballGuy!

[TrpnBils]

I found what I believe to be a Revolutionary War era 3# cannonball this morning at a colonial era river ford where we have found Spanish silver and a few colonial coins and large cents lately. I have a couple of questions for you (or whoever):

Diameter is measuring 2.86" after hammering off some of the rust which matches up with the 3# data I found, BUT the weight is up a couple of ounces at at 3lbs 4oz using a kitchen scale. How much of the increase there can be accounted for by the rust and/or the fact that it's been submerged in water for potentially up to ~250 years....can they retain water after submersion?

The photo below is immediately after I got home this morning and before the rust was knocked off which accounts for some irregularities in the surface in that photo. Looks to be perfectly spherical though now that it has been beat up a little.

 

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[TheCannonballGuy]

First... please pardon me for feeling the need to clarify some definitions for some forum readers, who might confuse the meaning of the terms corrosion and concretion. Those terms are extremely important in accurately measuring a metal ball's "true" diameter. Rust-corrosion (corrosion means "eating-away") causes metal objects to weigh less, not more. Rust-concretion, which is a "building-on" or "sticking-to" -- is the opposite of corrosion. Concretion on an object's surface causes the object to weigh more than it ought to.

Try using a digital Postal Shipping scale. Household scales are notoriously inaccurate.

If the 3 pounds 4 ounces weight for your ball turns out to be accurate, it is not a cannonball. A 2.84"-diameter ("3-Pounder caliber) cannonball weighed 3 pounds 1 ounce, or sometimes a bit less, due to the presence of internal casting-flaw airbubbles... but never more than 3 pounds 1 ounce, unless it's got a LOT of rust/dirt-concretion stuck to it.

I should mention... no Steel cannonballs were used in North America, just simple cast-iron. The difference is important, because steel is a denser alloy than simple cast-iron, weighing about 10% more than simple cast-iron. So, for example, if an "iron" ball weighs more than the cannonball weight charts say it should, it is a Steel ball, and therefore it is not a cannonball.
www.civilwarartillery.com/shottables.htm

 

[TrpnBils]

Thanks - I have access to a more accurate scale at work and I'll take it in with me tomorrow. Does the fact that it was submerged in water affect the weight at all? I know this is a different material, but I'm thinking of something like concrete that does soak up water even though it appears to be solid.

 

[NOLA_Ken]

Iron relics will absorb water, over time, which is why you want to make very sure they are completely dried out before hot wax sealing.

 

[Dug]

Iron relics will absorb water, over time, which is why you want to make very sure they are completely dried out before hot wax sealing.

I would not dry them in a fire in the event there is an explosive charge inside.

 

[callicles]

You can just let it sit out in an open, dry area for a few months. As time goes by, you'll see the iron pushing up beads of liquid rust that looks similar to tree sap. It may take more than a few months depending. But as time goes by you can see it and monitor it. Great job!!

 

[sutphin]

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