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Bubbles in wax


#1

You master casters out there can maybe settle a question for the
rest of us…

How big does an internal air bubble in a casting wax have to be
before it can cause a problem in a casting?

In other words, do poppy-seed-sized (say,1/2mm) bubbles inside the
wax cause issues? Mustard-seed-sized (1mm)? You get the idea.

Thanks
Noel


#2

The strength of the wax around a bubble will determine if the bubble
pops the vacuum process. The strength of the wax around a bubble
depends upon how deep the bubble is in the wax and the natural
strength of the wax. The deeper the bubble is in the wax the
stronger the wax around it will be.

The best way to protect a casting from being being damaged during
the vacuum investment process is to vacuum the wax before investing.
That way any damage may be repaired before investment.

Lee Epperson


#3

If you don’t vacuum de-bubble, it doesn’t matter.

Paf Dvorak


#4

Change your wax. It’s cheap and easy.


#5

Noel,

All bubbles in wax are a problem for casting. The air is pulled out
of the wax when it is pulled out of the investment leaving a hole in
the final product.

You master casters out there can maybe settle a question for the rest
of us…

How big does an internal air bubble in a casting wax have to be
before it can cause a problem in a casting?

In other words, do poppy-seed-sized (say,1/2mm) bubbles inside the
wax cause issues? Mustard-seed-sized (1mm)? You get the idea.

Thanks
Noel


#6

Noel- It’s mostly an issue of how close to the surface they are. We
strive for bubble free waxes. If we get a small one or two we’ll just
repair them in the wax. Otherwise they go into the trash or back into
the pot.

If you are consistently getting bubbles in injected waxes, It’s time
to address your pot and injector.

Have fun and make lots of jewelry.

Jo Haemer
timothywgreen.com


#7
In other words, do poppy-seed-sized (say,1/2mm) bubbles inside the
wax cause issues? Mustard-seed-sized (1mm)? You get the idea. 

If the bubbles are near enough to the surface that they can blow out
under vacuum and then fill with investment, they will be a problem,
otherwise, probably not. I’d still get to the bottom of it. If you
are talking about injection wax, I’m guessing that the wax pot is
under pressure all the time. Try releasing the pressure while it is
not in immediate use. Over time and under pressure, the wax can get
dissolved gases in it, sort of like a can of Pepsi. Shoot the wax,
the pressure is released and the dissolved gas forms bubbles. Your
wax is getting the bends and then freezing.

Dave Phelps


#8

Any size can depends on how close to the surface


#9

Hi, Noel. Great question. And the only real answer is, if you end up
with an investment inclusion than it was too big. Let’s get into
more detail though, and look at why an internal bubble is a problem.
The biggest potential problem with an internal bubble is that when
the wax is covered in investment, and then vacuumed, the vacuum will
cause the bubble to pop and the investment will go into the void
left by the bubble. So the real issue is when the bubble is close in
proximity to the surface of the wax. This creates more potential for
the bubble to pop and investment to enter. A bubble that is deeper
inside a medium to thick part, may not be too much of an issue.
Ifthe bubble pops, it could just have a very small pin hole letting
the air out. This tiny hole could inhibit any investment from
entering. But there is no real method for knowing when there will be
a problem and when there won’t be. The best suggestion is to
eliminate any air bubbles and not to worry about it.

Best regards,
Patrick Sage
Rio Grande
Product Manager


#10

We have always used the criteria that if one can see the bubble when
holding the wax up to a light, it will be disruptive.

Lois