I agree with Joe Lovato as well. I have seen the phenomenon of
investment getting sucked into a pore in the wax and leaving an
investment filled pocket in the final casting many times, especially
in large heavy pieces such as figurines and holloware fittings.
This can be remedied by careful inspection of each wax prior to
treeing and investing, particularly by holding each and every wax up
to a strong light, which will clearly show you any air pockets in the
wax pattern. Often these can easily be filled on a piece when they
occur in an area without detail. Otherwise, I just chuck it and make a
good one. Vacuuming your molten wax will also help cut down on these
defects
Another misconception is that jagged, geometric shaped voids which
sometimes occur on the surface of some castings are the result of
broken off investment. These are most often caused by trapped air
bubbles in the wax which do not have a pinhole opening to the surface,
and burst under vacuum during investing. I have places waxes with
these defects under a vacuum and had the same result on the surface of
the wax, some burst, some don’t.
Checking each piece under a strong light and tossing those with
bubbles is the best way to minimize these types of defects. I have
almost never seen a defect I could attribute to broken off investment
in almost 15 years of casting, no matter how intricate the pattern.
Mark Moretti
Fredericksburg, VA
@Mark1164
Hi Mark, Actually, you are agreeing with my statements exactly as I
had stated them in the beginning in relationship to the post I was
answering.Joe Lovato and a few others were trying to make a point
that there were many other causes ,which can be true. Like in your
experience of 15 years and my experience of 30+ years, wax air
pockets and streaks cause more problems than anything else and
careful wax inspection, mold venting,will solve this problem.
Investment break off has been a very rare occurance in my experience
and if this is happening particularly on heavier castings, It can
usually be resolved by using a different investment ratio ( 38/100)
instead of 40/100
Daniel Grandi
Hi Dan, You mentioned in an earlier post that it is possible to mix
investment too much. Do you perhaps mean, too long, or do you believe
there is a physical or chemical disadvantage to doing so. Also you
mentioned the use of wax wash. Do you use this on carved and
injection wax? What do you think the benefits are to using wax wash?
Thank you. John, J.A.Henkel Co., Inc., Moldmaking Casting Finishing
Hi Dan, You mentioned in an earlier post that it is possible to mix
investment too much. Did you perhaps mean, too long, or do you
believe there is a physical or chemical disadvantage to doing so. I am
always interested in learning as much as I can about investment.
Thank you. John, J.A.Henkel Co., Inc., Moldmaking Casting Finishing
Hi John, I believe I meant it can be a problem if you go past the
overall time recomended when investing. I am Presently Using ORO Vest
as an investment and they recommend that you are done investing at 9
minutes and to move your flasks off the machine quickly.
We invest 6 4x7 flasks at one time, and we had problems moving the
flasks off the machine quickly … ( We have about 15 seconds to move
all 6) I bought many heavy plastic Pizza pans and cut away an area of
the pan where the pipe goes through the top of the nvesting table.
Now, What we do is put the 6 flasks on the Pizza Pan and when the mix
is ready to pour, we move the pizza pan with all 6 flasks onto the
table. When the Investing is done in 9 minutes, it takes us 5 seconds
to move all six flasks at one time.
What we accomplished by doing this is that we eliminated the
investment cracking problem we occasionaly had on some flasks that
were moved individually closer to the 10 minute mark. This investment
cracking would look like a flash of metal around the top of the tree
and is mostly caused by moving the flask onto a drying table too
slowly. The Pizza Pan fixed the problem.
Your other question was about using wetwash , and I just replied on
Orchid at length about it’s benefits and what to watch for as far as
pit falls.
Hey folks on Orchid, I have to say that John Henkel Is a very
knowledgeable person in this field. He is an excellent mold maker and
caster as well and other than myself ( Racecar Jewelry Co.) he is one
of the few caster/ mold makers I would recommend . I have met john
at a few of the machinery shows over the years .
Best wishes to all.
Daniel Grandi