Preserving A Cannonball

Shane-1

Hows it going everyone, I was given a cannonball some time ago, it was found in a river bed and is destroyed with rust, in fact it is practically flaking to pieces! I am wondering of any of ye would know of any ways I could stop this and try and preserve it some bit? Maybe like painting it with a certain paint or something? Thank you.

Degsy

Shane-1 wrote: »

Hows it going everyone, I was given a cannonball some time ago, it was found in a river bed and is destroyed with rust, in fact it is practically flaking to pieces! I am wondering of any of ye would know of any ways I could stop this and try and preserve it some bit? Maybe like painting it with a certain paint or something? Thank you.

Maybe black hammerite?

enda1

Well to be honest you're probably best off getting rid of every trace of rust, then just keeping it indoors. Though I'm saying this NOT from an antique collectors perspective so maybe this is a faux pas.

Scawgeen

I agree with the last poster clean it down with a fine wire brush or steel wool (not brillo) and rub in linseed oil and keep it in the house.

Dr Strange

Submerse it for a couple of weeks in petrol. That is a common way of styopping the salts that cause rust in ground finds. If you want you can also use an electrolyte bath afterwards. If professional help is needed I know that the conservators in the National Museum are very helpful.

Shane-1

Thanks everyone for your help, I would be concerned about working off the rust as it appears to have decended into one big ball of rust, it is cracking in half too, disaster!

I have another one, far smaller which is holding up in perfect condition, which is bizarre as they were found in similar contexts, the well preserved one was found in a river bed whereas the other was found on the shoreline, I wonder if this has made the difference

enda1

Well the one in the sea would rust far quicker so I wouldn't be too surprised at the difference. The salt in the sea facilitates the corrosion much more than the conditions in a freshwater river + the cannon ball has a greater surface area + the sea would have far more erosive power than a river bed. Combination of all these things I guess.

How do you know it is a cannon ball by the way if its just a ball of rust? But I suppose what else could it be ?

Shane-1

that is actually quite a good question! I suppose I couldnt have any proof as such of what they are

The large, rusted one is identified as a cannonball by its material which is of solid lead or someother similar metal, its shape and its size, it is exceptionally big.

The smaller one is lead also, and shaped the same but can be identified more by the context of its discovery. It was found along with several more in the river bed at the base of one of the walls of Limerick Castle back when they were draining the river a few years back. It also has a small dent which I'm supposing is from its impact against the wall.

enda1

Are you sure they are lead!?

Lead doesn't rust first of all, seeing as how rust is the common term for iron oxide. It does oxidise however but to a dull greyish colour which actually protects the underlying metal, much in the same way as aluminium. Think that all victorian water pipes were made form lead so they must have been able withstand the corrosiveness of water for a very long time!

I'd suggest measuring the two balls diameters, and weighing htem to work out the density. Then you can tell basicly what metal they are made from.

I think you'll find the large one is made of iron, and the small one may be lead from your description.

cochineal

Hello,

I'm a conservator ex. of the National Museum and I'm currently putting together a course on the care of objects (metals, wood, etc.) found in marine or riverine environments that will be held early next year in the Curragh. It's aimed at divers and marine archaeologists but anyone can come along. I'll let everyone in this forum know all the details once arrangements have been finalized.

Shane-1

enda1 wrote: »

Are you sure they are lead!?

Lead doesn't rust first of all, seeing as how rust is the common term for iron oxide. It does oxidise however but to a dull greyish colour which actually protects the underlying metal, much in the same way as aluminium. Think that all victorian water pipes were made form lead so they must have been able withstand the corrosiveness of water for a very long time!

I'd suggest measuring the two balls diameters, and weighing htem to work out the density. Then you can tell basicly what metal they are made from.

I think you'll find the large one is made of iron, and the small one may be lead from your description.

Ah yes, that seems to make sense Had'nt thought of it like that before, cheers

cochineal

By the way, this cannonball is obviously an archaeological find and as such, you will require a license from the National Museum to work on it, ie. a license to alter. You should be consulting an archaeological conservator as all finds deposited with the museum must be conserved prior to deposition. Your excavation license application should have stipulated who your company usually use, so refer to this. The only thing that you should do is keep it in 2 sealed clear "zipper" style polyethylene bags with as much silica gel as you can fit in, temporarily store it in the driest room you have, and get it to a conservator a.s.a.p. I would not recommend using any preparatory solutions such as hammerite or linseed oil as this may interfere with the conservation process. Don't be afraid to ring the National Museum conservation department in Collins Barracks for advice, they are very helpful. By the way, iron rusts red and if it has any metal core left, it is magnetic. Lead "oxidizes" i.e. corrodes in oxygen, to form a greyish passivating layer of corrosion products.

Degsy

Musket balls would've been lead witha diameter of .5-1inch or so.
Cannonballs would certainly be iron and obviously much larger.