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Interesting little tips about casting


#1

What is the best way to remove air bubbles from investment before
casting, other than using the vacuum method?

If you have any interesting little tips about casting I’m sure there
is many people out there who are interested. Thanks, Ray.


#2
What is the best way to remove air bubbles from investment before
casting, other than using the vacuum method? 

You could try this - take a 3cm square piece of timber about 10cm
long. Take off the squre corners with a plane. Drill out along its
length so that it can securely fit a tapered screw on a polishing
lathe. Place your canister with investment on a board so that one end
rests upon the wooden block. Turn on the lathe and the vibrations
will bring most air bubbles to the surface.

Haven’t tried it but it should work.
Roger


#3

You can eliminate some air bubbles by tapping the invested flask
sharply on the table and using debubblising sprays on the pattern
but to be honest using a vacuum table beats any technique that
doesn’t involve a vacuum table.

All the best
Jen


#4
What is the best way to remove air bubbles from investment before
casting, other than using the vacuum method? If you have any
interesting little tips about casting I'm sure there is many people
out there who are interested. Thanks, Ray. 

What’s the best way without a vacuum? Don’t put them there in the
first place.

Mix your plaster, paint it onto your model with a soft thick brush,
put the model and rubber sprue base into the flask, then use the
bombs away method to fill the flask.

*FYI: The bombs away method is pouring your liquid from a height so
that you get a very thin stream of liquid. You pour your liquid so
that it hits the model, and fills the flask. There will be no bubbles
if you get the height right and the stream thickness.

Or you could use a hand massager, this also works, but I’ve been
accused of being kinky :wink:

Regards Charles A.


#5
What is the best way to remove air bubbles from investment before
casting, other than using the vacuum method? 

With the wax model attached to the sprue base, paint the surface of
the wax with a de-bubbleising liquid, blow off the excess, then paint
the surface with the mixed up investment with a small paint brush,
getting in all the nooks and crannies. Blow the surface gently so
there are no surface bubbles and so it is covered with investment.
Put the wax model back into the flask. Poor the investment into the
flask and do not vibrate- I find that vibrating can cause any bubbles
in the investment to gravitate to the wax. This is the best method I
have found when a vacuum is not available.

Cheers
Lee


#6

I believe in the olden days, they just painted several layers
directly (and carefully) on the piece to completely cover it with
the investment material. By being careful they would avoid air
bubbles. As long as air bubbles don’t touch the piece (or its
sprues), it doesn’t much matter if they are anywhere else in the
flask.


#7

Over the years I have cast in many different low tech situation. To
get rid of bubbles I have set the flask on a small board with rods
under it so it moves when you drum on it with sticks (paint brush
ends). Set on a toilet and flushed (not enough vibration). I have
gently rattled a stick in between two flasks. You can also get a
small vibrator made for casting dentist use them. The main thing I
have found is you need a gentle, steady tapping on the side ant top,
do not over do it as you can create bubbles.

I still use one of the last two technique today as I do not have a
vacuum set up I am old school. I have a small centrifugal casting
machine I got in 1974 when I first started doing casting and it is
all I use. Also remember to use the debubblizer.

I taught a casting class once with no casting machine and it was a
blast the only thing I did not get to do with the class was sling
casting as the parking lot was full of nice cars :wink: and the school
said we could not take the torch out there. We did sand casting,
cuddle bone, ingot casting and last but not least they carved wax
real thin and we did a direct pour. All good learning experience. Low
tech old school is good clean fun!

Have fun casting
Lauren


#8

I have taught casting in different places - Adult Ed school room,
studio, Ghost Ranch. Find that after all the debubblizer is totally
dry, gently pour the investment down the side of the flask, rolling
to make sure all areas are covered as it fills. Generally was able to
use the electric vibrator made for casting, and always the debubble
side of my Aqua-Vac. But in the absence of the electric or my vacuum
caster, while at Ghost Ranch, would secure the flask in my left hand
and gently tap the sides of the flask with the handle of a screw
driver…but gently enough not to dislodge the wax item from the
base. Have had that happen - rinse and start over!!!

Rose Marie Christison