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Stir rods of choice?


#1

Today in the shop we were talking about using stir rods when casting
and which type is better, carbon, quartz or ceramic. Personally I
have prefered quartz just because they don’t deteriorate like
carbon, but they do seem to break more easily. I have worried about
the carbon rods breaking down and leaving little bits of carbon
floating in the metal. To me one of the primary jobs of the stir rod
is to pick up little bits of floating crud (mostly flux) out of the
molten metal before you cast. I’m wondering which type people prefer
and if one seems to be a better crud picker-upper than another?

Mark


#2
and which type is better, carbon, quartz or ceramic. 

My prefered stir rod is a fresh twig, ripped of an bush a minute
before. It purifies the metal also. Has something to do with the
gases the are produced while the stick is in the molten medal. I am
sure someone can explain that better than me.


#3

I never liked using a stir rod, I have a very large acetylene
welding torch and after the metal is melted I add flux and move the
arm of the centrifugal caster to release the pin, I jiggle the arm
and gently slosh the metal in the crucible and with the force of the
flame detritus is stuck to the side of the crucible by the flux and
I have done this for over 12 years and over a million sterling
castings. Although I do far smaller amounts of silver now, stirring
350 grams of sterling with rod was not fun.

Richard Hart G.G.
Jewelers Gallery
Denver, Co.


#4

I use plain old bamboo chop sticks as stirring rods. They don’t
break, and do the job well.

Alma


#5

Just to be awkward I use all 3 materials. I suppose carbon would be
my choice as it degasses the metal and removes impurities but it
conducts heat [to the hands] well and small dia rods are rather
brittle. For quartz and alumina I use lengths of tube as they are
stronger than the equivalent size rod. When I used to do aluminium
alloy casting I used a large home make carbon spoon to scoop dross
from the surface as we didnt want other metals in contact and it was
impractical to make a quartz glass spoon.

Nick


#6

Hi Nick,

I suppose carbon would be my choice as it degasses the metal and
removes impurities... 

I did not know that about carbon, good to know. I assumed it was used
mainly because it could take the heat. I am always making an effort
to keep everything as super clean as possible (which is not very
sometimes) and not to introduce anything into the melt, it concerned
me that the carbon stir rods broke down. But your degassing comment
makes me rethink.

Thanks,
Mark


#7

Greetings:

I did not know that about carbon, good to know. I assumed it was
used mainly because it could take the heat. I am always making an
effort to keep everything as super clean as possible (which is not
very sometimes) and not to introduce anything into the melt, it
concerned me that the carbon stir rods broke down. But your
degassing comment makes me rethink. 

The carbon rods break down into carbon monoxide (CO), and take
oxygen away with it as they do so. Most helpful.

Regards,
Brian.