Lead objects-- preservation and safety tips?

[PMah]

I have accumulated some lead objects without really trying, and I do not know much about preservation and safety.  As a kid, I had some US Civil War-era lead minie balls, which were not then white-gray, but clearly most are now.(Sadly, that also means my "100+ year old" bullets are now "150+", along with me! 
    Similar patina seems to come with with ancient objects such as sling bullets, seals, tokens.  Is a sealant wax a good idea?  What about mylar vs other wrappers? 
  I searched the board and found very little detailed info, so guidance would be appreciated!  I suppose I should have done my research before rummaging through the objects!

[v-drome]

Hi PJM.  I am afraid this reply will not be very satisfying.  Lead is in my opinion the most difficult metal to deal with, as it is so reactive.  A single artifact can have four or more different types of corrosion, and anything you do to mitigate one type can make the others worse.  In addition, the corrosion often incorporates the surface details, so you can lose a lot if you clean it, even with a soft toothbrush, unless it is very loose dirt above a sound surface.  A lot of my lead came from a seaside environment, so chloride is a problem.  I will sometimes try to reduce the chloride with a brief soak in distilled water, sometimes with a very small amount of sodium bicarbonate to check any acidity, but even this can cause problems if other types of corrosion are present, some of which need moisture to do their damage.  I have also tried, on occasion, to apply a very small amount of mineral oil after soaking and drying, to keep the moisture out.  I am not an expert or a chemical engineer, so hopefully others may weigh in.  I try to avoid any cleaning of lead, unless there is obvious active corrosion.  And I wash my hands a lot.  My understanding is that the salts of lead are more of a hazard than the pure lead itself.  Posting photos may help in getting further advice.  Good luck!

[SC]

I have cleaned the white powder off some lead items.  Things like lead musket balls, not items where there was danger of losing details.

To do so I went outside, put on a dust mask, stood upwind of the item (made sure my dog, or anyone else, was not sitting downwind), and brushed with a toothbrush.  I made sure to clean the brush and then shake the mask, also downwind from me.  I then washed my hands well, twice.

The powder is usually on the item when I got them.  I don't have a problem with lead corrosion spreading.  I don't live in a particularly humid region though.

SC

[PMah]

Thank you both for replies.  I am going to do more research before attempting anything.  I am also in a seaside area, so humidity is a concern. I would prefer to take preservation steps that woukd not require repetition for decades.    Since lead is soft, prone to corrosion, and at least somewhat of a health concer, I hope to find a good balance. 
  Lead objects were often very real artifacts of daily life, so in some ways they are a more direct connection to past people in ways that more refined objects are not..

[n.igma]

Storage of lead artifacts is also an issue to be considered ....   http://nautarch.tamu.edu/CRL/conservationmanual/File14.htm

STORAGE
Lead is particularly susceptible to organic acids, such as acetic acid, humic acid, and tannic acid. Lead artifacts, therefore, should not be stored in oak cabinets or drawers. If so, even small concentrations of vapors of these acids can initiate corrosion, which progresses rapidly. To be safe, lead should by stored in sealed containers or polyethylene bags.

Also p. 12-13 of the pdf on on conservation of archaeological metalwork down load from ... http://hist-met.org/images/Storage_Display_Metalwork_2ndPP.pdf

[v-drome]

Hi, n.igma.  Thank you for the additional information.  This a topic I am very interested in.  I liked the second article in the post above, but I have some concerns about the first.  The author suggests putting lead in hydrochloric acid, which, I think, creates more lead chloride.  They state that they are considering "lightly corroded" objects, not the heavily corroded (and fragile) objects I have had to deal with, but why anyone would want to treat lightly corroded lead that way, I don't know.  I am open to correction if I am wrong!  I have never had good results from HCL, and it seems almost impossible to completely remove from the artifact, post treatment.

Best regards, V-drome

[n.igma]

... I liked the second article in the post above, but I have some concerns about the first.  The author suggests putting lead in hydrochloric acid, which, I think, creates more lead chloride.

In posting the links to the articles I was more focused on the long term storage issue. 

Cleaning and preservation of lead artifacts is not an area in which I have any expertise, but the acid soak seemed a pretty drastic step to me.

I note that it proposes a strongly diluted (10%) HCl solution and maybe the intent is to use weakly acidic solution for cleaning? In which case far milder acid (diluted lemon juice, weak acetic acid etc) would be equally or more effective, certainly safer? 

Even so, I'd suggest that treating any metal with acid needs to be done with extreme caution and care after trialing on a small inconspicuous surface area of the artifact in question.

Certainly immersion in an acid solution is not something I'd recommend.

[v-drome]

 .  Good point.  I think they may talking about lead sheathing, bullets and other substantial artifacts.  Both articles had very useful information.

Jimi

[PMah]

Thanks for the additional info!

[v-drome]

Here is the kind of thing I have had to deal with.  Here is a tiny (9mm) lead tessera with a standing figure.  The patina is a loose brown/gray layer containing all the detail.  It easily flakes off revealing soft white powder underneath.  There is really nothing I know of to do but to keep it dry and photograph it before it is gone.  

[SC]

I am no expert in lead but from what I understand the brown, though it looks like dirt, is a kind of stable patina.  The white is the active corrosion, which can unfortunately spread, and the dark grey is the base lead itself.

I think you are right in that there is little to do but keep it dry and handle it as little as possible.

SC