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Experiment with Casting


#1

Hi all

I definitely don’t want to revive the debate on centrifugal v
vacuum casting but I do want to experiment with casting on a
small scale.

I have cast with cuttlefish (fun but smelly) and Delft clay
(less smelly and more repeatable but model shape is too limited).

I don’t want to purchase a vacuum table to debubble the
investment but have noted the adverse comments on debubbling
additives – can I not just vibrate the investment and then the
invested flask as I am told it was done ages ago?

Assuming I can get a decent investment then how to cast. Gravity
works for cuttlefish and clay, why not for investment (with or
without steam assist). I can probably improvise centrifugal but
wonder at the need.

My parameters are Sterling Silver only, max flask size probably
3*4, no more than 4 pieces per tree and one or two casts per week

  • I did say small scale didn’t I.

I could probably spend a lot of time experimenting but I would
rather cut stone ( this metal thing get’s more fun as I learn
more though).

Note from my sig I am in England so second user or favorite
sources are usually a bit far for me to travel> TIA

Andy Parker, Agate House Lapidary
Ulverston, Cumbria, England
http://www.netcomuk.co.uk/~andyp


#2

Andy, when I learned a little about casting a few years ago,
we did it cengtrifugally (didn’t have a vacum setup) and vibrated
the flask after we filled it. It worked, but didn’t always do an
absolutely perfect job. Two thing that seemed to help were 1)
we drew the water from the tap and let it sit for a few days be
fore using it – which helped rid it of at least some of the air;
and 2). we painted the model with a (diilute) detergent solution,
which seemed to help prevent bubbles from forming on the model.
And, of course, when mixing the investment, try to avoid
stirring a lot of air into it! Margaret @Margaret_Malm


#3

Dear Andy,

I use a vacuum caster in my shop so I do have my biases. I have
also had great success with centrifugal casting.

The vibrator will get most of the bubbles out so you can manage
the piece. If you give the wax a good coating of denatured
alcohol first this will reduce the bubbles even further. You can
buy manufactured debubblizer, but it does the same thing.

Casting with cuttlebone (or any other gravity feed) is different
from cent. or vac. casting in that molten metal wants to ball
together to much, therefore you need some kind of force to get
the metal into the details of the mold. If you’re casting a
fairly simple piece, and you don’t mind the texture, cuttlebone
will work just fine.

Tim McCreight has a great book that explains all you need to
know about every type of casting: “Practical Casting, A Studio
Reference”. Brynmorgen Press, 33 Woodland Rd., Cape Elizabeth ,
Maine 04107; (207)767-6059.


#4

Hi Andy, Definitely vibrate the plaster and then the flask
(without a debubblizer). Gravity doesn’t work too well, so use
steam. Have fun. Tom Arnold


#5

Hi Andy:

As I’m sure you are fast discovering, it’s not tyhe metal or the
stones that put you in the poor house, it’s the tools!

I would suggest that for your needs, investing in a centrifigal
casting machine is a really good idea. You should look for ma
used one if you can get it.

You “can” cast without a vacuum, but you will have bubbles to
clean out of your work–a lot of bubbles. Remember, you only
have about 8-10 minutes from the time that you start mixing the
investment, to the time it begins to set up.

Also a “gravity pour” may not get into all the detail of your
work before the metal starts to soldify. Pouring 50% more than
the required metal may be a solution to keep it molten long
enough to reach all the cavaties. You’ll just have to
experiment.

What you need to consider is how much your time is worth? Try
pouring a few gravity pours over a range of works that hsave
different amounts of detail. If you finds that you have so many
bubbles in the metal that it takes forever to clean up, then
invest in some tools that get the job done properly.

Cheers

Virginia


#6

Dear Andy:

Yes you can certainly coat your mounted waxes with debubblizer
solution (a wetting agent), wait about 10-15 min., invest and
vibrate your flasks. With practice, you should have no trouble
with bubbles. As for the method of casting, you’ll find a simple
broken arm centrifical machine mounted in a large wash tub to do
quite nicley. I prefer Kerr’s satin cast 20. I don’t know if
it’s available on your side of the Atlantic however. If you
don’t wish to spend the $300. or so for a new machine, you can
likely find a used one from someone in the jewelery trade or the
dental trade as they use a very simular model. Hope this helps;
Steve Klepinger


#7

Hi Andy,

Regarding your question about investing without a vacuum - you

may want to try making a thin solution of investment and painting
it onto your waxes. Let it dry and do a couple layers,
especially over details, where bubbles get caught, until all your
surfaces are smooth. Then fill the flask with a regular solution
of investment, give the surface that the flask is setting on a
couple wacks, and you should eliminate most bubbles. By the way,
this is a good technique for those of us who vacuum, as a first
step for very detailed waxes, such as those celtic bands that are
so popular now.

Sarah
Sarah Graham Metalsmithing