I am new to the list, and have just been lurking out here. When
the question of vacuum casting vs centrifugal casting came up, I
just have to throw in my 2 cents and that is about what it might
be worth. I agree with almost every thing that Peter Rowe had to
say. I have been casting since the very eary 1970s, and I have
been teaching silver casting to Junior High and adults for over
25 years. I believe that centrifugal casting is the only way to
cast sterling silver. I do not cast much gold.
I have to disgree with those who recommend vacuum casting. I
have both in my shop. I use the vacuum casting machine only to
vacuum my investment to eliminate bubbles. I believe suppliers
want to sell vacuum casters because they sell for over $700.00
and there is more profit than a less than $400.00 broken arm!
The vacuum caster that will cast 1000s of casting per day also
cost thousands of dollars. Usually over $10,000.00 and most over
$20,000.00.
I will also tell what a centrifugal caster can do that a vacuum
caster can not do. I cast 10 to 20 items (everything from rings
to pendents) in one 2 1/2" x 3 1/2" flask and I cast 10 flasks
nearly every day and I get 100 percent of every cast, even if I
am casting natural objects, such as Mountain Alder “pinecones”.
I have never talked to anyone that could come close to this
volume with a $800.00 vacuum caster. I cast all ten flasks in
less than an hour and if I am in a real hurry I can do all 10 in
a half hour, by my self. And, I will agree once again with
Peter about the density and higher quaulity of the castings.
I taught junior high students to use both casters for 13 years
and adults in private classes that I teach in my own classrooms;
one in Boulder and one Loveland, Colorado. I have never had one
person get their nuckles scraped and especially never had anyone
burned with flying silver. Of course, I followed the
manufacturers suggestion and built a box around my centrifugal
casters, but common sense would have told me to do that!
Man, the more I type about this the hotter I get. There is just
so much misout there, that a new person to casting
has to pick and choose what they want to use. I have cast
100,000 castings in the past 20 years by my self. If you doubt
this I will give you references! I beleive that, for a beginner,
steam casting is better than vacuum casting. It will only cost
you about $50.00 to make a kiln and caster, buy a torch and some
investment and start casting. Your casting will be as good or
better than vacuum casting. There was a very good article in
Lapidary Journal in the past six months. I only disagreed with
that author with the elaborate equipment he thought everyone had
to use.
I have taught many kids and adults to steam cast with a flower
pot for a kiln and a jar lid packed with paper towels for the
caster. And they got the same results, but more consistant than
vacuum casting. Steam is more powerful than vacuum and gives a
more dense casting.
So, if your doing this for a hobby or small business try steam!
If you are going to do a lot of casting use centrifugal casting,
but buy a vacuum caster for debubblerizing your investment. Just
do not use it for casting. Think about it for a moment. What
actually moves the silver into the mold. It takes some kind of
force. The weight of the small amount metal and the quick rate
of freezing (cooling) prevent just pouring into the mold. You
must force it in to the mold and I believe the more force the
better the casting.
A vacuum caster only has the force of the air in the atmosphere
that is “sucked” back in to the bell jar after you have created
a vacuum in the jar. There is no magical force flowing, it is
just the amount of air that rushes back in to the bell jar! And,
that is not much. Many years ago I read an article in one of the
rockhound magazines about a man who built a vacuum machine out
of a vacuum sweeper. It makes more sense to me than a vacuum
caster, because it can move more air to “suck” the metal in to
the mold. I still think the power of steam does a better job.
The great thing about teach junior high kids is that they will
do every thing just opposite of what you tell them. I have had
10 to 20 waxes placed in one flask, and with only a 16th of an
inch of investment over the top of the highest waxes. I have
never had a back of flask break out! May be I am just lucky, but
I perfer to think it is because all the great advances in all
the supplies that I have seen in the past 25 years. Investments
these days are unbelievable.
Remember, I cast mainly silver, just a little gold, but a lot
of silver every week. Probably more than most. I am not
bragging, because it gets tiring and boring at times. I just
want you to know that I am a caster and have been for 25 years.
If you are a manufacturer of vacuum casters or sell them please
do not flame me either. I have two vacuum casters that I would
never do with out! I just do not use them for casting and still
recomend them for every caster if they can afford them. Or, I
suggest they buy a vacuum caster first, cast enough on it to
make enough money to buy a real caster, a centrifugal caster.
Or, of course you can always buy one of those $20,000.00 vacuum
casters. I have never got to use one of those. I bet they are
great!
If you wish you can visit my site of the Colorado Academy of
Silversmithing and Art Metal at http://www.frii.com/~dnorris.
We can carry on this discussion on my questbook or we can chat
using ICQ. My number is 20830163.
I am sorry if I have come on too strong, but I have been
teaching casting for too long not to have very strong opinions
about the ways I teach. I hope I have not hurt any ones
feelings!
Don Norris
@Donald_Norris
PO Box 2433 Estes Park, CO 80517
http://www.frii.com/~dnorris