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Using metal wires in investment during casting


#1

I am doing silver casting that has some very small holes I would
rather put in during the wax process rather than have to drill after
the metal is cast. Is there something I can use to “keep the hole
open”. I find that when the hole is particularly small, sometimes the
investment doesn’t flow into these little spaces.

I have heard that there is a metal which can be used which will not
"stick" to the silver and can be pulled out after the silver has
cooled. If true, what kind is it and how can I get it?

Also, I am just starting to supply my home studio (most of my work
is done in a lab at school). Is there some sort of investment that
"self debubbleizes" so that I can do that portion of the process at
home without access to the bell jar?


#2

Debora, As far as debubleizing, you can use your copper tongs (or
similar tool) to tap the flask and get out a lot of the bubbles. I
have a vacuum machine and it can create a lot more bubbles that it
gets out. If you tap the flask for a while that gets out most of the
bubbles.

Chris Slater
@Chris_Slater1


#3

i cast pieces from rubber molds that have thin silver tubing for
hinges and investing with a vaccuum pump should fill the inside of
the tube, you must orientate the opening toward the top of the flask,
and gently pound on the investing table as hard as you can without
dislodging the wax model to get the air out, richard hart, denver,


#4

Hi there, you can try painting investment into your model before you
put the flask over it, I’ve got a couple waxes infront of me I’m
going to do that with today, as they’re very delicate. The problem
with metal rods is that if the holes are deep, and not perfectly
straight, the wire may get stuck in the final piece. I’ll probably
recive some flak over this, but investment is basiclly just
over-priced plaster, you can thin it a bit to get higher detail, but
it will take longer to set up and dry. Don’t over thin it, that can
ruin the batch, but 10-15% extra water probably wont hurt it, and
shoiuld make it so it flows into the small holes. I’d use the thiner
bath for the “painting” and then once that’s done, mix a regular
batch for the flask. Also, the point of the vacuum is to remove air
trapped in the mix from the water you use, and mixing. Careful
mixing, and using room temp water that’s been sitting out for a
couple days should help a lot. Also, I’ve seen people invest without
a vacuum, but I’ve always been told to use it. I’m in the same boat
as you, I have access to a great lab at school, but basics only at my
own shop. sigh anyone wanna give me 5 grand for a jewelry studio?
heh…nope didn’t think so :stuck_out_tongue:

Anyways good luck with it
-Doug
Albuquerque, NM


#5

Use broken drill bits in the molds to keep the holes open. I have
been told you can also leave them in for the casting and then remove
them after the casting.I have not done this personally so be sure to
run a test before you make any major comittment. Let me know how it
works out. Frank Goss


#6

I think you can try using pencil lead (graphite rods) to fill up the
holes in wax pattern available at stationary stores, I know 0.5mm
pencil leads are available.you have not specified the size of the
holes.

Umesh Chauhan


#7

Debra, Years ago an associate of mine was casting items he wanted
holes in and used pencil graphite. It comes in many sizes, from very
small to up to 1/8 inch, and as I remember, did not stick to the
metal castings! You can use long pieces in order for the investment
to ‘grasp’. Thomas


#8

You can use pencil graphite leads. But not every brand are in pure
graphite, they may be of plasticised something. To be sure, try to
burn one with a soldering flame. If it burns, its plastics. If not, you
can even use this one.


#9

Debubbleizing is very effectively accomplished by using a small hand
held electric massage unit against the side of the invested flask. I
have found that the best technique is to to remove the rubber cup
from the stem of the massager and use the stem itself to transmit
the vibration. This technique also is very effective in causing the
investment to flow more freely when pouring the investment into the
flask. These small massage units are available from time to time in
the Dollar stores here in California and elsewhere in the U.S. Some
are battery powered and some are plug-ins. The plug-ins are the
better choice, although either will do a credible job. It is
important to remember that one should hold the flask firmly on the
sprue former base while using the massager with the other hand,
otherwise the investment is apt to flow out from the base. It is
best to have the left over investment handy so that the flask can be
topped off in the event of leakage at the base. I should mention
that this technique should be preceded by thoroughly vibrating or
vacuuming the investment before pouring into the flask. Works for me
! Ron at Mills Gem, Los Osos, CA.


#10
I am doing silver casting that has some very small holes I would
rather put in during the wax process rather than have to drill after
the metal is cast. Is there something I can use to "keep the hole
open". I find that when the hole is particularly small, sometimes the
investment doesn't flow into these little spaces. 
I have heard that there is a metal which can be used which will not
"stick" to the silver and can be pulled out after the silver has
cooled. If true, what kind is it and how can I get it? 

The classical way of maintaining a hole or tube lumen when casting
was to insert a graphite (pencil lead) rod into the hole. These were
obtainable in stationery stores. Unfortunately these solid graphite
rods are now quite difficult to find (except for rather thick ones
used in drafting) having been replaced with plasticized rods which
would break up during burn out. You might however try titanium wires
of the correct diameter if obtainable from your supply houses.
Extend them beyond the holes so that they can be gripped by the
investment and thus maintain their postional relationship. Since the
silver will not stick to the wires, you should be able to separate
these from the casting/

    Also, I am just starting to supply my home studio (most of my
work is done in a lab at school). Is there some sort of investment
that "self debubbleizes" so that I can do that portion of the
process at home without access to the bell jar? 

This can be accomplished rather easily! There are any number of
liquid debubblizers which are available. After the pattern is sprued
you can paint this liquid on the pattern with a very soft paint
brush, blow off the excess and then “paint” on the mixed investment.
Next flow in the investment along the inner side of the ring, to
minimize entrapment of air. Let that set. When you take the set ring
to school, soak it in water prior to putting it in the burn-out
oven, so that it heats up gradually and will not crack. P.S. Any
surface reducing liquid can be used in a pinch if you’re unable to
obtain the bebubblizer. Hope this helps. Dr. J.Z. Dule