Neycraft centrifuge problems

Don't ask me to source this, but I heard a few years back that the
x-rays of King Tuts gold mask shows that it was made in various
pieces and had to be cast. Now THAT would have been interesting to
see. 

I saw the thing in person in the Cairo museum a few years ago. It’s
mounted up on a clear plexiglass mounting, allowing you to look up
inside the thing. It’s hollow, clearly hammered/formed sheet metal.
And you’re correct, it’s pieced together from a number of pieces. But
they sure did not look cast. I’'m pretty sure this was hand worked
sheet metal, not casting. What’s interesting is that the various
parts appear to have been stuck together by “sewing” with wire, as
well as “gluing” with what looked like black pitch. From the
outside, you see no clue to this structure, as all these seams are
below the inlaid areas. My guess is that the inlay work could have
been done first, before the various sections were connected. That
would have made inlay easier, and would have allowed more workmen to
sork simultaneously on the thing.

I would have loved to take pictures of the mask when I was there,
but at the time (and maybe still, I don’t know), they were not
allowing photographs in that gallery. Other parts of the museum, yes,
but not that room. Perhaps to keep photos proprietary, or perhaps to
prevent light damage to pigments (on other pieces in the room) or the
like. The room was otherwise rather carefully lit with just what was
needed to see the things in it. Not bright light, so I’m guessing the
concern was damage from camera flash. But penlights were OK, and I
happened to have one with me, so I got a pretty good look up inside
Tut’s mask. Yes, the plexi case was in the way, so I might be wrong,
but it sure looked totally fabricated to me, as is apparently the
case with virtually all the other larger gold egyptian goods of the
period, at least so far as I remember…

Peter Rowe

At the Progress Tool auction in L.A. a year ago, I bought a 28 in.
long casting arm that will accommodate a 8 1/2 in. long casting
cylinder. Once I make my casting shroud a bit larger, I should be
able to put my "monster" casting arm on my existing Vigor base,
and spin some seriously large castings! 

I think you will find out rather quickly why this large flask arm
never really caught on. The speed of your machine will decrease
significantly as the mass on the end of the arm and the length of
the arm increase the needed power to get the same velocity. SO your
spring will not have enough oomph to quickly accelerate the crucible
and flask and you will start seeing more casting problems like no
fills.

James Binnion
James Binnion Metal Arts

I likewise have never heard of any North American culture that was
into metal casting. When I was researching lost wax casting history
I never found any details on centrifugal casting any where. There are
any number of pictures in the Spanish literature written by the
priests that accompanied the Conquistadors that went into central
and south America and I know of no pictures showing sling casting
although there is a lot of beautiful gold casting work in the gold
museums of Peru, Columbia, Panama, and Costa Rica. I used a picture
of a casting from Columbia (that I purchased rights to) on the cover
of my book on casting. The museums often have descriptions of the
casting process that may not be correct. I have never determined how
they got the mold to fill without vents or a permeable investment.
(Any out there?)

For a description of the use of lost wax casting for bronze statues
see the Autobiography of Benvenito Chelini (sp).

The Greeks were also very accomplished casters around 450 BC. There
were at least a dozen foundries in Athens and Bronze was the
preferred material for statuary although most of it got melted down
by the next tyrant or when they needed weapons.

The Chinese were somewhat later in using lost wax casting because
they were very accomplished in making piece molds.

At one time I was told that someone in England was writing a very
definitive history of lost wax casting but I have never heard that
the book was completed.

Fred Sias
www.woodsmerepress.com

Hi Jay Whaley,

At the Progress Tool auction in L.A. a year ago, I bought a 28 in.
long casting arm that will accommodate a 8 1/2 in. long casting
cylinder. Once I make my casting shroud a bit larger, I should be
able to put my "monster" casting arm on my existing Vigor base,
and spin some seriously large castings! 

I would really like to have a long casting arm like yo urs, to take
this size flask, Is there any way to determine who the mak er is, so
I could buy one? ( I have 2 bases,and just replaced the broke n
spring in one. The spring came from Richard Lucas at Lucas Dental
Co., a very good person to deal with! )

thanks, Andy

I get the Orchid RSS feed which precludes individual email addresses
so if Alma Rand is still looking for an answer to her Neycraft
Cradle Slide Syndrome somebody might forward my solution on to her.

Staples carries heavy duty “Binder Clips”: black spring clips with a
little handle on each side for leverage. The 19mm version fits
easily but firmly over the carriage rail on the Neycraft casting
machine. I keep one on each rail. When I insert the flask and push
the carriage forward I move the binder clips forward to trap the
carriage between them and the flask. The work perfectly.

Les Brown

I had some dental tech friends in Oslo, Norway I stayed with one
summer, and I watched them “sling cast” gold crowns in their high
tech lab. Even though they had very advanced casting machines, they
preferred this “primitive” method to do all their castings of crowns.
Even though they whipped the flask in its chain suspended cradle over
their heads, they never lost a gram of gold!

Since modern jewelry can be technically sophisticated or primitive
in appearance, it’s all jewelry after all, and any process that
produces a desired result would seem to validate the process. Whether
an automatic induction casting machine or a charcoal fire and a clay
mold is utilized, jewelry is the end product.

Jay Whaley

As I said, it's subtle. You cannot see the differences (other than
if you've got bad porosity) in the casting, much less the finished
item. But the spin cast metal can sometimes be distinctly
stronger. Key word there is "sometimes"... 

All of Peter’s post is why I personally prefer centrifugal casting.
Intellectually I know that vacuum will do the job, but (properly
done) nothing is going to stop a centrifuge from doing it’s duty.
Just me…

I believe I read that theory in one of Tim Mccreight’s books years
ago. I found another article that stated that dentists in the 12th
century use to pour the gold then spin it overhead by chains to
centrifugally cast.

Lost-Wax Casting: Old, New, and Inexpensive Methods

HI All,

Once upon a time, one of the production jewelers I worked for had a
custom made “monster” spin caster. (It’d do a couple of pounds,
IIRC) He used the coil spring from a garage-door lifter as the main
body spring. Worked great, even if the thing was terrifying to watch.
Boosted that huge arm up to speed just about as quickly as a
standard sized machine.

Just do NOT screw up with that thing. (He also added fiberglass
threads to his investment to help hold it together against the
strain.)

FWIW,
Brian.

Leslie, Thanks for the suggestion about the Binder Clips. I have
learned that the problem I was having with the crucible sliding out
of place was due to the fact that I had been sold a crucible that
was nota genuine Neycraft crucible. The nose was the wrong shape and
size, and even after grinding it down, I was having problems. I have
since ordered new crucibles from Otto Frei, which are genuine
Neycraft crucibles and they fit perfectly. So far no sliding. If I
ever do have a problem, I will follow your suggestion and attach
Binder Clips to each of the rails.

Thanks for taking time to let me know about this.
Alma

I believe I read that theory in one of Tim Mccreight's books years
ago. I found another article that stated that dentists in the 12th
century use to pour the gold then spin it overhead by chains to
centrifugally cast. 

The link you gave goes to fellow Orchidian Fred Sias’s book, where I
describes this method, but used by early 20th century dentists, not
12th century. Traditional dental fillings done prior to this involved
literally hammering successive layers of pure gold into a drilled out
cavity, rather than cast and glued inlays (what’s done today). And I
rather expect that in the 12th century, filling cavities with gold
was not so common. (consider George Washington’s well documented
dental wear, wooden false teeth…)

And while Tim does show this method (as I alluded to when I first
commented on your post), he doesn’t specifically call this an ancient
method, nor is there documentation therein to that effect. It’s
merely an illustration for students.

Peter

I believe I read that theory in one of Tim Mccreight's books years
ago. I found another article that stated that dentists in the 12th
century use to pour the gold then spin it overhead by chains to
centrifugally cast. 

I think you need to re-read that, the passage you link to refers to
Dr Taggert and Dentists in the early 20th century not 12th.

Jim

James Binnion
James Binnion Metal Arts

I likewise have never heard of any North American culture that was
into metal casting. 

It might have been South American Indians that I read.

I think you need to re-read that, the passage you link to refers
to Dr Taggert and Dentists in the early 20th century not 12th. 

I stand corrected on the article. Thank you for pointing that out.