Re: Pewter... lead?
- From: Deirdre <finch.enteract@xxxxxxx>
- Date: Thu, 03 Nov 2005 20:23:42 -0600
Custos Custodum wrote:
>
> On Wed, 02 Nov 2005 14:46:08 -0600, Deirdre <finch.enteract@xxxxxxx>
> wrote:
> >Is that a relatively recent state of affairs?
> >I've some old pewter pieces that I've been
> >reluctant to use because I was concerned
> >about lead content and was told the percen-
> >tage couldn't be determined without damage
> >to the piece.
> >
> Isn't there anything small enough to fit into an SEM?
A scanning electron microscope? No, there
really isn't...they're plates, pitchers and the
like. I've used such for imaging, but what pro-
cedure would one use to determine composition?
I tried, once, taking a really small paring (seriously
small, less than 300 microns square...) from the
bottom of the pitcher down to the beam line, but
all I could determine was that there was a com-
bination of tin with a trace of copper (~70% and 1%
respectively). The balance, I presumed to be lead
(setting up to just measure lead is too time con-
suming and expensive for a non-project satisfy-
the-curiosity measurement, so I used derivation
instead).
There was also something else in there which I
couldn't identify, but someone later conjectured
might have been Antimony...and there was no real
way to tell the proportions because I wasn't set
up to look for it at the time and didn't notice it
until long after the run time window was past.
The real problem however, stems from the slush
factor in the data...+/-10% at best...so there's a
lot of weasel room. Even with all that, the mea-
surement only told the tale of the _outer_ bot-
tom of one piece, I've no way of knowing what
the interior might have been exposed to or if it's
identical.
> My Oxford Science Dictionary informs me that if the proportion of lead
> is less than about 35%, it will remain in 'solid solution' - i.e. it
> won't leech out - even in the presence of the usual acids found in
> food and drink.
Hm. Well, assuming the outside bounds of the
range, (tin 60%, copper a false signal) it would
seem that these bits and pieces might be just
skirting the edge of that...or over it. Or not, it
might be 80% tin, 10% copper, 9% antimony and
1% lead and reasonably safe.
If 35% is the magic number, I guess the safest
solution is just to leave them on the shelf and
remember to have them dusted regularly.
Deirdre
.
- References:
- Pewter... lead?
- From: NT
- Re: Pewter... lead?
- From: grey$hawk
- Re: Pewter... lead?
- From: Deirdre
- Pewter... lead?
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