getting rid of lead solder

[medusa]

I have an old enamel brooch which I intend re-enamelling. It has clearly been through the wars although the front is good despite extensive enamel loss. I could see that it had had a pin hinge and catch soldered and probably re-soldered onto the back at some point so I ground down with a round diamond burr until I thought I was hitting silver. I then applied a bit of heat and saw it was pretty discoloured still, so went at it again. Still discoloured. Repeated and then smoothed the surface with radial wheels so I could be sure it wasn't some kind of discolouration from the grinder. Still there.

I recall James saying that you can dissolve lead solder by leaving in hydrochloric, but I'm a bit anxious about damaging the piece. Despite the damage, it is good quality by a collectable maker but the last thing I want is to fire it and have lead contamination bubbling up through the enamel.

I'm attaching a pic, so any advice is appreciated.4440

[Goldsmith]

To remove lead from most base metals get yourself some drain cleaner, I use Spirits of Salts drain cleaner, this is about 30% hydrochloric acid solution and is available from most hardware stores, I usually only have small antiques that have lead on to remove, so I just let them soak for a while in a pyrex bowl with enough spirits of salts to cover the infected area, and after an hour or so the lead just dissolves, or sometimes quicker. The lead turns to dust and when dry and can be brushed off.
Do it in open air though, as there are nasty fumes from the drain cleaner which is an acid formula, don't stand over it when opening the bottle and pouring it, rubber gloves are also needed.

James

[medusa]

thanks James, When you say the lead turns to dust, does that mean I should expect large pits in the silver, and if so, how deep would they go?

[Goldsmith]

thanks James, When you say the lead turns to dust, does that mean I should expect large pits in the silver, and if so, how deep would they go?

I really depends on the earlier solderings. If you can find a clear jamjar and use that for the Spirits of Salts, you can hold it up and see how the acid reacts to the lead. For that job you only need about half inch in a jamjar, you should see it bubble a little when the item is first added. Tie a bit of copper wire around the piece so that you can lift it out ,wash it and inspect it at intervals. I have used this method many times on antiques that are worth many thousands. If your job does have lead on it then it needs to be cleaned before you can restore it.

James

[medusa]

Cheers James,

I'll have a hunt for the salts tomorrow and let you know how it goes, but first, can you tell me how I will know if all the lead is gone?

[ps_bond]

IIRC, Homebase sell Spirits of Salt (HCl) still. HG branded? I don't think B&Q do it, but I may be wrong. Having said that, I think brick acid might be hydrochloric from memory, albeit very dilute.

[Goldsmith]

Cheers James,

I'll have a hunt for the salts tomorrow and let you know how it goes, but first, can you tell me how I will know if all the lead is gone?

After using the Salts clean the area with some abrasive or an abrasive rubber wheel and you will see clean metal.

This is the type of stuff you need, there are many makes, mine is made by Hiltons but this is on Amazon;http://www.amazon.co.uk/Kilrock-Spirits-Limescale-Plughole-Unblocker/dp/B007OUI5D8/ref=sr_1_1?ie=UTF8&qid=1361912769&sr=8-1
Most DIY stores will stock a variety as plumbers love it for clearing drains and plugholes quickly.

[medusa]

After using the Salts clean the area with some abrasive or an abrasive rubber wheel and you will see clean metal.

This is the type of stuff you need, there are many makes, mine is made by Hiltons but this is on Amazon;http://www.amazon.co.uk/Kilrock-Spirits-Limescale-Plughole-Unblocker/dp/B007OUI5D8/ref=sr_1_1?ie=UTF8&qid=1361912769&sr=8-1
Most DIY stores will stock a variety as plumbers love it for clearing drains and plugholes quickly.

Thanks James, should I double check it by gently heating it? Because after grinding quite a way down with the diamond burr, the metal looked nice and clean, but it was only when I heated it that the black patches re-appeared. I'm worried about how deep the lead goes.

[Goldsmith]

Thanks James, should I double check it by gently heating it? Because after grinding quite a way down with the diamond burr, the metal looked nice and clean, but it was only when I heated it that the black patches re-appeared. I'm worried about how deep the lead goes.

Are you sure that you haven't already got rid of the lead by grinding?, does it smooth over or bubble slightly when you heat it with the torch?
If the lead burns into the surface it gives an appearance of something similar to rough etching. I would use a scraper to scrape the surface as if it's lead the scrapings will be softer than silver. If you want to test perhaps you could scrape off a piece, sit it on a bit of scrap and heat it.If it's lead it will melt quicker than if it's silver.

James

[medusa]

I ground it down but when I heated it I got the dark patches you can see in the attached photo. I thought the presence of those indicated that some solder (and I was assuming lead solder because of it's age) remained. I thought the problem with lead solder is that it soaks into the silver and I don't want it soaking in so deep it comes through to the front. Or am I just being over cautious?

[Goldsmith]

It's difficult to be certain without actually seeing it. I would get some Spirits of salts, soak it for an hour or so, it will not harm the silver if you left it in it for many hours, but if there is any lead it will attack it and be quite obvious to the eye.

James

[medusa]

Thanks James,

I'll hit the hardware stores tomorrow!