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Embedding sterling into lead free pewter?


#1

Hi everyone,

I’m attempting to learn lead free pewter casting, and need a way to
add a bail to my casting (it is not possible to drill a hole in the
casting).

Due to the difference in melting temperatures, my idea was to use a
sterling bail with a post attached, where I could embed the post
into the pewter while casting. Unfortunately, I have read about
pewter contaminating/pitting sterling, and also that there may be a
chemical reaction between the two which might affect the wearer.

I have 3 upcoming shows in the next couple of weeks, and I’d love to
have this new product available, so I don’t have much time for
experimentation, and certainly no time to “test drive” wearing the
pendant for months.

Does anyone have any ideas for me?

Thank you so very much,
Robin


#2

Hi Robin,

Worst comes to worst, you could try the same trick using titanium
wire.

I’ve cast around it with bronze, at 2000F, so pewter shouldn’t make
any impression on it at all.

Just make sure you’ve got some sort of mechanical grab going with
the pewter. There will be no metal-to-metal bond whatsoever.

FWIW,
Brian


#3

I would use another metal, tinned copper or tinned mild steel.


#4

I have been making models for pewter casting for over 20 years now.
Silver will work but you do not need to solder it together if you
are only going to use it once for a mold. Try a two part epoxy.
liquid steel will take the molding temperatures. Also is good for
building up the backs of things that are too thin to mold.

I also most of the time use copper or bronze instead of silver
because I like to save my originals so I can duplicate the mold when
it wears out and I then have pennies in the master and not dollars
sitting around. Pewter is great for making models in for molding.
Nickel plate everything if you want a super smooth surface on your
pieces. Most of the time I do not bother…

My experience is that the epoxy holds up for a one shot mold. then
you will need to re epoxy it for the next one most of the time.

Vernon Wilson
Panama Bay Jewelers


#5
Unfortunately, I have read about pewter contaminating/pitting
sterling, and also that there may be a chemical reaction between
the two which might affect the wearer. 

The problem with tin (pewter is usually almost pure tin with a trace
of copper) or lead, or alloys of the two, and silver, is that if
there are bits of these alloys on the silver, AND YOU THEN HEAT THE
SILVER to SILVER SOLDERING TEMPS, the lower melting metals will melt,
alloy with, and then sink into the silver, creating what can be
disastrous pits. But this only happens when the silver is heated to
substantially higher than the melting points of the pewter or lead.

You’re not doing that here, as you’re only heating enough to melt
the pewter, not to melt any silver alloy. So no pitting to worry
about.

You can make your bails in silver, designed so they fit into a
suitable part of your mold so they’re held in position by the mold,
and they should have some part of silver that will extend into the
pewter, preferably with a shape that will “lock” into the pewter so
the joint can be purely mechanical in nature, rather than requiring
strength in a “solder” joint or similar bond where the tin would have
to “wet” the silver. You cast the pewter normally, it flows around
and locks into the silver, and voila, you’ve got your bail.

There should be no chemical reaction here to worry about. Both
pewter and silver as safe for the wearer, and the combination is no
different.

Peter