Hi Marshall,
(SNIP)
I need to know where I can find “IT”
solder.
You could try Thomsons Enamels
Thompson Enamels, 650 Colfax Avenue, Bellevue, KEN 41073, (606-291-3800):
(or P.O. Box 310, Newport, KY 41072):
My partner, Dee Fontans does a lot of enameling and uses hard and even
medium solder to bond findings to her works and then enamels them
afterwards (she sometimes even hard solders with medium after enameling).
She fire the enamel at about 1500 degrees F and pulls the enamel out as
soon as the surface has fused properly. So you mayt not need IT at all. If
you really need some you could take, say 10 grams of sterling and add a
half a gram of brass to it, ally it and try that. There is also the option
of fusing your sterling parts together, fusing if done carefullly and using
flux can be as clean looking as soldering (practice involved in this one)
Also, a while back I tried to pour a sterling ingot with little luck. I
heated up the cast iron mold thing in the kiln till it was red-hot. I then
tried to pour the liquid silver, Some went in, but most of the silver
solidified on top.
Was the silver in the mold thing? Normally I just melt in a ceramic
crucible and then pour it. (see later comments on keeping oxygen away). You
don’t need to pre-heat a mold unless it is for very large amounts of metal.
Just rub a little oil on it (I hate sooted molds-agh-unecessary and
mucky-the oil converts to a thin layer of soot when the hot metal hit it).
If your metal freezes in the mold it may be the fault of your pouring. If
your pour and it freezes three times in a row maybe you need to heat your
mold, but by then your mold will have been heated by pouring the metal into
it…
Does anybody know an easy way to grain sterling with little or no
equipment? Just a torch and maybe a crucible?
You don’t need to grain (granulate) silver for casting it. It is an extra
stage to contaminate it with oxygen and as seen in the following comments I
prefer to take a lump and roll it out into foil before melting to speed the
melting time.
And maybe a pointer on how
to degas it so that I don’t build up oxygen in the crystalline structure?
You could try adding just the teeniest smidgen of zinc to your melt a
moment before casting it (big refineries do this with large ingots),
however you really shouldn’t have dissolved oxygen in your metal if you
melt correctly.
Most pitting in cast silver alloys is due to dissolved oxygen coming out of
solution. (and yes there are other gases that can dissolve and a few other
causes-usually too high a melt temperature and/or mold temperature can
result in damaged surfaces [boiled looking])
Silver and silver alloys love to absorb oxygen while at high temperatures,
where it is dissolved just like CO2 in soda pop-you can’t see it until you
change the pressure conditions when the gas comes out of solution like when
you take the top off the soda bottle. (in Lab conditions 1 kg of fine
silver can dissolve 20kg of Oxygen by weight-luckily sterling is not as
bad-I don’t have a clue why she’s not getting pits with fine)
If you have allowed oxygen to be dissolved in the silver while molten then
it comes out as the temperature drops and the metal solidifies, tending to
occur and be sqeezed towards the gate/sprue button area of the model thus
resulting in pits there.
Avoidance: in industry sterling melts are done in vacuums, under ammonia
atmospheres and so on. Sometimes an induction melting crucible is used,
load the crucible, put a thin layer of charcoal powder over the metal (eats
oxygen), put a lid on it until molten. In a small studio one has to use
other methods.
Do all you can to limit oxygen access at high temperatures to your metal.
Keep the time it is hot/molten and able to absorb oxygen to a minimum.
Preheat the crucible intensely (like a long long time) and use a slightly
gassy flame-note the slightly-if you are leaving black soots around you
need way more oxygen in the flame, what you are looking for is a slightly
yellowish flicker at the end of the inner blue cone-assuming an
oxy-acetyelen or oxy-propane rig.
Watch the edges of the crucible, they should glow evenly, if it darkens in
one spot then oxygen is sliding into the crucible.
Use a bushy, large flame and slant it towards the crucible so it makes a
lid to protect the melt, a sheet of flame as a shield. In Germany the
actual cast is sometimes done through a pure (yellow) gas flame as well.
Roll your metal out as thin as it will get and roll it up into coils like
mini rolled rugs for melting. This increases the surface area and reduces
the melting time dramatically. Keep the melt covered by the gassy flame at
all times and consider adding a chunk of charcoal to the crucible to
consume oxygen, slide the charcoal to the back of the crucible and it
should be left behind in a centrifugal cast. Cast into an appropriate
flask temperature. The shorter the melting time the less oxygen can be
absorbed by the metal. Do not add to much oxygen to the flame to shorten
melting time-it is counterproductive-you need that reducing flame.
Do not remove the flame to add flux, if you have to add flux then insert an
iron or graphite rod into the flame to warm, dip it into powdered flux and
then insert the rod through the flame to add flux-do not remove the flame
which is protecting the melt. If you have melted very well you may not need
to make any flux additions, the melt will be smooth and shiny like a
mirror-in that case you did well and just cast with it.
Scrap sterling cast metal may have dissolved oxygen locked into it from
previous exposure at high temperatures, it seems to be cumulative.
Some people add a ‘flux’ to the melt, ammominum chloride and so on to
‘degas’ it, I feel this is not useful. In refineries they sometimes add the
teeniest little smidgion (1 gram per 5+ kg of sterling) of zinc to the melt
just before casting to ‘degas’ it.
When melting metal: Oxygen is your enemy.
Good luck. Also try posting the question on the rec.crafts.jewelry news
group and direct it to Peter Rowe, I respect his opinion on these things a
great deal. (ie; calling Peter Rowe!!)
Charles
Brain Press
Box 1624, Ste M
Calgary, Alberta, T2P 2L7
Canada
tel: 403-263-3955
fax: 403-283-9053
Email: @Charles_Lewton-Brain