Hi everybody! Can anybody across the ocean give me some advise about
casting and soldering iron? I’m trying but the results are not good.
The casting is not perfect and very delicate in the sense that the
pieces break very easily while I don’t like to use silver solder
because I don’t want to see the white col our. I’m trying to contact
you because here in Italy nobody is really interest ed in
experimenting new things. Jewellery has to be traditional! Thank you
very much for any help! Ciao Cristina
As for the casting, I know that even the best commercial cast iron is
on the brittle side, it’s one of the material’s signature traits. As
for joining, you have the choice of learning to forge weld, or solder
the material with a brass brazing rod (places that sell welding
supplies have them in a variety of types, you might have to
experiment a bit, as I can’t even guess at what might be available in
Italy). Try seeking out a traditional blacksmith, they can show you
a few tricks for ferrous metals that most jewelers never need to
learn.
Ron Charlotte – Gainesville, FL
@Ron_Charlotte1 OR afn03234@afn.org
I have been told by smiths much more experienced than I that cast
iron is too brittle to forge and therefore to forge weld. However
your brass brazing rod suggestion is right on. You can also look at
the Artist Blacksmith Association website www.abana.org. There is a
forum there or another forum site www.keenjunk.com. The smiths there
should be able to help you with any forging problem you might have.
Linda
Try seeking out a traditional blacksmith, they can show you a few tricks for ferrous metals that most jewelers never need to learn.
Hi Ron and I can’t remember who the original poster was who asked
the questions about iron. I am a traditional blacksmith (as well as
goldsmith, silversmith . . .just call me a “metalsmith” please). But
as a blacksmith, I wouldn’t necessarily know about cast iron other
than the problems associated with repairing it. But I’ve also had a
little experience in casting iron. I used resin bonded sand or
ceramic shell for molds, and poured quite large (150 pounds plus),
but the metalurgy still applies. Here are some considerations.
First, you are correct, Ron. Cast iron is, by nature, brittle. The
ancient Chinese had a method of super-annealing it to give it
somewhat maleable characteristics. Otherwise, it is essentially
crystaline. The curse (or blessing) is carbon. Pure iron is nearly
carbon free. Mild steel has a little carbon, tool steel has a little
more, and cast iron has about as much carbon as can dissolve in
molten iron. Carbon lends the structure around and throughout which
the iron builds a rigid structure. (This is an oversimplification,
of course. Ferrous Metalurgy is a comlex science, and I’m no
metalurgist). Now suppose you took pure iron, or as close to it as
can be aquired short of reagent pure. Such a source might be the
soft iron wire you find jewelers using, which I believe might also be
available in a hardware store. You would need to melt it in a carbon
free environment. An electro melt wouldn’t work, it has a graphite
crucible. A torch wouldn’t be much better, there is enough unburned
carbon in the flame to contribute to the metal’s embrittlement. If
you melted in a crucible with a lid, with the heat source coming from
outside the crucible, you could practically cast the iron without the
addition of much carbon. You would probably do this in an investment
material that was designed for high temperatures, such as the
non-crystobolite, 2 part investments used for platinum and other
high temperature metals. After pouring the metal, you’d want to
allow the flask to cool to room temperature before breaking away the
plaster. This sounds complicated, but it’s really not. You would
only need to have a clay crucible with a lid and a box built of
refractory material, such as could be made using refractory brick
used in lining kilns. Don’t confuse refractory brick with insulating
brick. Refractory brick is light and spongy, and reflects heat,
whereas insulation brick is dense and is used for both structural
strenth and to slow conduction of heat. Your heat source could be a
torch with a large tip pointed into a hole in the brick box. Check
Steve Midget’s designs for kilns to make Mokume Gane. You could, of
course, build a “foundry”. There are many good sites on the Internet
on how to do this. But remember, if you’re making jewelry, you
probably don’t need to melt more than an ounce or two of metal at a
time. If you are casting more than this, why not look into having a
commercial casting company produce it for you?
But finally, I need to ask a question, and it’s a somewhat pointed
one. It is this: What characteristics of iron are you interested
in? Is is the color? The fact that it is IRON with all it’s
attendant associations or the novelty of it as a jeweler’s material?
The novelty for it’s marketing promise? Novelty for novelty sake, to
distinguish yourself within this market burgeoning with product and
novelty, novelty, novelty? Just plain old curiosity? If you answer
yes to any but this last question, you get a “D” for my course.
Here’s why. When goldsmiths (and the platinum guild) decided
platinum was where they needed or wanted to go, they didn’t bother to
learn diddly about it’s characteristics or what had been done with
it in the past. They made bulky, heavy, wasteful designs. They
carved wax like goldsmiths and drove platinum casters crazy. They
developed cobalt alloys to avoid the problems of ignorant and lazy
platinumsmithing, thereby compromising the integrity of the material.
And they seldom if ever made anything as beautiful as had been made
in platinum eighty years before. Historically, cast iron was used
often for decorative purposes, and if it also supplied structural
support, it was appropriately massive where it needed to be. Iron is
the malleable sister of cast iron and it was quite an accomplishment
to make it at one time. If you simply melt iron ore, with
carbon-based fuels, you’ll have cast iron. How people have
discovered how to get relatively carbon free iron out of iron ore is
a fascinating story. Read Cyril Stanley Smith’s “A History of
Metalology”. But pure iron’s plasticity can be directly acted upon
and it is best exploited for that characteristic. Catch my drift
here? You can do some things best with cast iron and some things
best by forging malleable iron. Design your jewelry with an
understanding of both the limits and the possibilities of your
materials. Either learn to forge iron, or use cast iron where it’s
brittle nature is irrelevant, or do what I hate to see jewelers do .
. . try to find some bit of technical know-how that will allow you to
short cut all this learning and thereby make things that might as
well be made of anything else. Sooner or later, some manufacturer
will knock off your successful designs and make them using powder
metallurgy or maybe even plastic. They won’t pay a craftsman to
facilitate manufacturing. They will pay an engineer, and they’ll pay
him only once.
David L. Huffman
Hi Christina, Cast iron will always be brittle, particularly in small
cross sections due to its crystalline nature. It cannot be easily
soldered and must be either brazed using brass rod which obviously
has colour implications, or welded - in either case a special flux is
necessary. Neither of these methods produce joins which are as strong
as the original metal due to the way the heat changes the metal
structure. You would probably achieve as good a bond using an epoxy
resin although, as the crystals of the iron are greasy in nature, I
would also try to make some form of mechanical retention such as
drilled holes which the glue could penetrate.
Best Wishes,
Ian
Ian W. Wright
Sheffield UK